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Characterizing the coseismic slip behaviors of earthquakes could offer a better understanding of regional crustal deformation and future seismic potential assessments. On 18 December 2023, an Mw 6.0 earthquake occurred on the Lajishan–Jishishan fault system (LJFS) in the northeastern Tibetan Plateau, causing serious damage and casualties. The seismogenic fault hosting this earthquake is not well constrained, as no surface rupture was identified in the field. To address this issue, in this study, we use Interferometric Synthetic Aperture Radar (InSAR) data to investigate the coseismic surface deformation of this earthquake and invert both ascending and descending line-of-sight observations to probe the seismogenic fault and its slip characteristics. The InSAR observations show up to ~6 cm surface uplift caused by the Jishishan earthquake, which is consistent with the thrust-dominated focal mechanism. A Bayesian-based dislocation modeling indicates that two fault models, with eastern and western dip orientations, could reasonably fit the InSAR observations. By calculating the coseismic Coulomb failure stress changes (∆CFS) induced by both fault models, we find that the east-dipping fault scenario could reasonably explain the aftershock distributions under the framework of stress triggering, while the west-dipping fault scenario produced a negative ∆CFS in the region of dense aftershocks. Integrating regional geological structures, we suggest that the seismogenic fault of the Jishishan earthquake, which strikes NNE with a dip of 56° to the east, may be either the Jishishan western margin fault or a secondary buried branch. The optimal finite-fault slip modeling shows that the coseismic slip was dominated by reverse slip and confined to a depth range between ~5 and 15 km. The released seismic moment is 1.61 × 1018 N·m, which is equivalent to an Mw 6.07 earthquake. While the Jishishan earthquake ruptured a fault segment of approximately 20 km, it only released a small part of the seismic moment that was accumulated along the 220 km long Lajishan–Jishishan fault system. The remaining segments of the Lajishan–Jishishan fault system still have the capability to generate moderate-to-large earthquakes in the future. [ABSTRACT FROM AUTHOR]

High-resolution topographic and stratigraphic datasets have been increasing applied in active fault investigation and seismic hazard assessment. There is a need for the comprehensive analysis of active faults on the basis of the correlating geomorphologic features and stratigraphic data. The integration of TLS and GPR was adopted to characterize the 3D geometry of the fault on the Maoyaba segment of Litang fault. The TLS was used to obtain the high-resolution topographic data for establishing the 3D surficial model of the fault. The 2D 250 MHz and 500 MHz GPR profiles were carried out to image the shallow geometry of the fault along four survey lines. In addition, the 3D GPR survey was performed by ten 2D 500 MHz GPR profiles with 1 m spacing. From the 2D and 3D GPR results, a wedge-shaped deformation zone of the electromagnetic wave was clearly found on the GPR profiles, and it was considered to be the main fault zone with a small graben structure. Three faults were identified on the main fault zone, and fault F1 and F3 were the boundary faults, while the fault F2 was the secondary fault. The subsurface geometry of the fault on the GPR interpreted results is consistent with the geomorphologic features of the TLS-derived data, and it indicates that the Maoyaba fault is a typical, normal fault. For reducing the environmental disruption and economic losses, GPR was the most optimal method for detecting the subsurface structures of active faults in the Litang fault with a non-destructive and cost-effective fashion. The 3D surface and subsurface geometry of the fault was interpreted from the integrated data of TLS and GPR. The fusion data also offers the chance for the subsurface structures of active faults on the GPR profiles to be better understood with its corresponding superficial features. The study results demonstrate that the integration of TLS and GPR has the capability to obtain the high-resolution micro geomorphology and shallow geometry of active faults on the Maoyaba segment of the Litang fault, and it also provides a future prospect for the integration of TLS and GPR, and is valuable for active fault investigation and seismic hazard assessment, especially in the Qinghai-Tibet Plateau area. [ABSTRACT FROM AUTHOR]

Active layer thickness (ALT) is a sensitive indicator of response to climate change. ALT has important influence on various aspects of the regional environment such as hydrological processes and vegetation. In this study, 57 ground-penetrating radar (GPR) sections were surveyed along the Qinghai–Tibet Engineering Corridor (QTEC) during 2018–2021, covering a total length of 58.5 km. The suitability of GPR-derived ALT was evaluated using in situ measurements and reference datasets, for which the bias and root mean square error were approximately −0.16 and 0.43 m, respectively. The GPR results show that the QTEC ALT was in the range of 1.25–6.70 m (mean: 2.49 ± 0.57 m). Observed ALT demonstrated pronounced spatial variability at both regional and fine scales. We developed a statistical estimation model that explicitly considers the soil thermal regime (i.e., ground thawing index, TIg), soil properties, and vegetation. This model was found suitable for simulating ALT over the QTEC, and it could explain 52% (R2 = 0.52) of ALT variability. The statistical model shows that a difference of 10 °C.d in T I g is equivalent to a change of 0.67 m in ALT, and an increase of 0.1 in the normalized difference vegetation index (NDVI) is equivalent to a decrease of 0.23 m in ALT. The fine-scale (<1 km) variation in ALT could account for 77.6% of the regional-scale (approximately 550 km) variation. These results provide a timely ALT benchmark along the QTEC, which can inform the construction and maintenance of engineering facilities along the QTEC. [ABSTRACT FROM AUTHOR]

The planetary boundary layer (PBL) over the Tibetan Plateau (TP) exerts a significant influence on regional and global climate, while its vertical structures of turbulence and evolution features remain poorly understood, largely due to the scarcity of observation. This study examines the vertical profile and daytime variation of turbulence dissipation rate (ε) in the PBL over the TP using the high-resolution (6 min and 120 m) measurements from the radar wind profiler (RWP) network, combined with the hourly data from the ERA5 reanalysis. Observational analyses show that the magnitude of ε below 3 km under all-sky conditions exhibits large spatial discrepancy over the six RWP sites over the TP. Particularly, the values of ε at Minfeng and Jiuquan over the northern TP and Dingri over the southern TP are roughly an order of magnitude greater than those at Lijiang, Ganzi and Hongyuan over the eastern TP. This could be partially attributed to the difference of land cover across the six RWP sites. In terms of the diurnal variation, ε rapidly intensifies from 0900 local standard time (LST) to 1400 LST, and then gradually levels off in the late afternoon. Under clear-sky conditions, both ε and planetary boundary layer height (zi) are greater, compared with cloudy-sky conditions. This reveals that clouds would suppress the turbulence development and deduce zi. In the lower PBL (0.2< z / zi <0.5, where z is the height above ground level), the dominant influential factor for the development of turbulence is the surface-air temperature difference (Ts – Ta). By comparison, in the upper PBL (0.6< z / zi <1.0), both the and vertical wind shear (VWS) affect the development of turbulence. Above the PBL (1.0< z / zi <2.0), the shear production resulting from VWS dominates the variation of turbulence. Under cloudy-sky conditions, clouds are found to decrease the surface total solar radiation, thereby reducing Ts – Ta and surface sensible heat flux. This weakened sensible heat flux tends to inhibit the turbulent motion within PBL especially in the lower PBL and decrease the growth rate of zi. On the other hand, the strong VWS induced by clouds enhances the turbulence above the PBL. The findings obtained here underscore the importance of RWP network in revealing the fine-scale structures of the PBL over the TP and gaining new insight into the PBL evolution. [ABSTRACT FROM AUTHOR]

The eastern slope of the Tibetan Plateau is a crucial corridor of water-vapor transport from the Tibetan Plateau to Eastern China. This is also a region with active cloud initiation, and the locally hatched cloud systems have a profound impact on the radiation budget and hydrological cycle over the downstream Sichuan Basin and the middle reach of the Yangtze River. It is noteworthy that there is a strong diversification in the characteristics and evolution of the ESTP cloud systems due to the complex terrain. Therefore, in this study, ground-based Ka-band millimeter-wave cloud radar measurements collected at the Ganzi (GZ), Litang (LT), Daocheng (DC), and Jiulong (JL) sites of the ESTP in 2019 were analyzed to compare the vertical structures of summer nonprecipitating clouds, including cloud occurrence frequency, radar reflectivity factor, cloud base height, cloud top height, and cloud thickness. The occurrence frequency exhibits two peaks on the ESTP with maximum values of ~20% (2–4 km) and 15% (7–9 km), respectively. The greatest (smallest) occurrence frequency occurs in the JL (GZ). The cloud occurrence frequency of all sites increases rapidly in the afternoon, and the occurrence frequency of the DC presents larger values at 2–4 km. In contrast, the occurrence frequency in the JL shows another increase from 2000 LT to midnight at 7–11 km. Stronger radar echoes occur most frequently in the LT at 5–7 km, and hydrometeor sizes and phase states vary dramatically in mixed-phase clouds. A small number of radar echoes occur at midnight in the JL. A characteristic bimodality of the cloud base height and top height for single-layer, double-layer, and triple-layer clouds was observed. Clouds show a higher base height in the GZ and higher top height in the JL. The ESTP is dominated by thin clouds with thicknesses of 200–400 m. The cloud base height, top height, and thickness exhibit an increase in the afternoon, and higher top height occurs more frequently from midnight to the next early morning in the JL because of its mountain-valley terrain. [ABSTRACT FROM AUTHOR]

Observations of vertical wind in Chongqing, a typical mountainous city in China, are important, but sparse and have low resolution. To obtain more wind profile data, this study matched the Aeolus track with ground-based wind observation sites in Chongqing in 2021. Based on the obtained results, verification and quality control studies were conducted on the wind observations of a wind profile radar (WPR) with radiosonde (RS) data, and a comparison of the Aeolus Mie-cloudy and Rayleigh-clear wind products with WPR data was then performed. The conclusions can be summarized as follows: (1) A clear correlation between the wind observations of WPR and RS was found, with a correlation coefficient (R) of 69.92%. Their root-mean-square deviation increased with height but decreased by 3 - 4 km. (2) After quality control of Gaussian filtering (GF) and empirical orthogonal function construction (EOFc, G = 87.23%) of the WPR data, the R between the WPR and RS reached 76.00% and 95.44%, respectively. The vertical distribution showed that GF could better retain the characteristics of WPR wind observations, but with limited improvement in decreasing deviations, whereas EOFc performed better in decreasing deviations, but considerably modified the original characteristics of the wind field, especially regarding intensive vertical wind shear in strong convective weather processes. (3) In terms of the differences between the Aeolus and WPR data, 56.0% and 67.8% deviations were observed between ± 5 m/s for Rayleigh-clear and Mie-cloudy winds vs. WPR winds, respectively. Vertically, the mean differences of both Rayleigh-clean and Mie-cloudy winds versus WPR winds appeared below 1.5 km, which is attributed to the prevailing quiet and small winds within the boundary layer in Chongqing, such that the movement of molecules and aerosols is mostly affected by irregular turbulence. Additionally, large mean differences of 4-8 km for Mie-cloudy versus WPR winds may be related to the high content of cloud liquid water in the middle troposphere, influenced by the topography of the Tibetan Plateau. (4) The differences in both Rayleigh-clear and Mie-cloudy versus WPR winds had changed. Deviations of 58.9% and 59.6% were concentrated between ±5m/s for Rayleigh-clear versus WPR winds with GF and EOFc quality control, respectively. In contrast, 69.1% and 70.2% of deviations appeared between ± 5 m/s for Rayleigh-clear versus WPR and EOFc WPR winds, respectively. These results shed light on the comprehensive applications of multi-source wind profile data in mountainous cities or areas with sparse ground-based wind observations. [ABSTRACT FROM AUTHOR]

The current deformation and stable state of slopes with historical shatter signs is a concern for engineering construction. Suspected landslide scarps were discovered at the rear edge of the Genie slope on the Tibetan Plateau during a field investigation. To qualitatively determine the current status of the surface deformation of this slope, this study used high-resolution optical remote sensing, airborne light detection and ranging (LiDAR), and interferometric synthetic aperture radar (InSAR) technologies for comprehensive analysis. The interpretation of high-resolution optical and airborne LiDAR data revealed that the rear edge of the slope exhibits three levels of scarps. However, no deformation was detected with differential InSAR (D-InSAR) analysis of ALOS-1 radar images from 2007 to 2008 or with Stacking-InSAR and small baseline subset InSAR (SBAS-InSAR) processing of Sentinel-1A radar images from 2017 to 2020. This study verified the credibility of the InSAR results using the standard deviation of the phase residuals, as well as in-borehole displacement monitoring data. A conceptual model of the slope was developed by combining field investigation, borehole coring, and horizontal exploratory tunnel data, and the results indicated that the slope is composed of steep anti-dip layered dolomite limestone and that the scarps at the trailing edges of the slope were caused by historical shallow toppling. Unlike previous remote sensing studies of deformed landslides, this paper argues that remote sensing results with reliable accuracy are also applicable to the study of undeformed slopes and can help make preliminary judgments about the stability of unexplored slopes. The study demonstrates that the long-term consistency of InSAR results in integrated remote sensing can serve as an indicator for assessing slope stability. [ABSTRACT FROM AUTHOR]

Three cases of microphysical characteristics and kinematic structures in the negative temperature region of summer mesoscale cloud systems over the eastern Tibetan Plateau (TP) were investigated using X-band dual-polarization radar. The time-height series of radar physical variables and mesoscale horizontal divergence δ ¯ derived by quasi-vertical profiles (QVPs) indicated that the dendritic growth layer (DGL, −20°C to −10°C) was ubiquitous, with large-value zones of KDP (specific differential phase), ZDR (differential reflectivity), or both, and corresponded to various dynamic fields (ascent or descent). Ascents in the DGL of cloud systems with vigorous vertical development were coincident with large-value zones of ZDR, signifying ice crystals with a large axis ratio, but with no obvious large values of KDP, which differs from previous findings. It is speculated that ascent in the DGL promoted ice crystals to undergo further growth before sinking. If there was descent in the DGL, a high echo top corresponded to large values of KDP, denoting a large number concentration of ice crystals; but with the echo top descending, small values of KDP formed. This is similar to previous results and reveals that a high echo top is conducive to the generation of ice crystals. When ice particles fall to low levels (−10°C to 0°C), they grow through riming, aggregation, or deposition, and may not be related to the kinematic structure. It is important to note that this study was only based on a limited number of cases and that further research is therefore needed. [ABSTRACT FROM AUTHOR]

Raindrop size distribution (DSD) observations with OTT PARSIVEL2 disdrometers at Dari and Delingha in the northeast of the Tibetan Plateau (TP) during summer 2019 and 2020 were utilized to investigate the DSD characteristics and DSD‐based polarimetric radar quantitative precipitation estimation (QPE) relations on the X, Ku, and Ka bands. The DSD characteristics were examined for different rain rates (R) and for stratiform and convective rainfall types. The raindrop spectra became wider and flatter as the R increased. Gamma parameters N0, μ, and λ (representing intercept, shape, and slope parameters, respectively) were smaller for convective compared to stratiform rainfall, corresponding to the broader and flatter convective raindrop spectra. The μ–λ and Dm–log10Nw relationships were also examined in our study. There was a significant μ–λ correlation, with a quadratic function relationship. The summer convective rainfall at both Dari and Delingha showed continental‐like clusters based on the Dm–log10Nw relationship. The DSD‐based two‐parameter polarimetric radar QPE relations (R(Zh, ZDR), R(KDP, ZDR)), and one‐parameter relations (R(Zh), R(KDP)) at the X, Ku, and Ka bands were proposed, and the R computed from DSD was implemented to evaluate these relations. The performance of two‐parameter models was stronger than that of one‐parameter models. Moreover, R(Zh, ZDR) and R(KDP, ZDR) performed better for the X and Ku bands, while the R(KDP, ZDR) model performed best for the Ka band. The ground‐based Ka/Ku band measurement Z at Dari was used to evaluate the Z–R and R−Dm QPE relations. The R−Dm relations had a better performance compared to the Z–R relations. The Ku radar‐derived R series are more consistent with the DSD measured counterparts. The research of the dual‐polarization radar parameter models is vital to develop radar QPE algorithms on the TP. Key Points: The raindrop spectra become wider and flatter as the R increases. Gamma parameters were smaller for convective than for stratiform rainfallThe summer convective rainfall at both Dari and Delingha showed continental‐like clustersThe performance of two‐parameter models (R(Zh, ZDR) and R(KDP, ZDR)) was stronger than that of one‐parameter models (R(Zh) and R(KDP)) [ABSTRACT FROM AUTHOR]

Located on the southeastern periphery of the Tibetan Plateau, the Xianshuihe fault (XSHF) is an active left-lateral strike-slip fault renowned for its frequent and intensive seismic activities. This highlights the necessity of employing advanced geodetic methodologies to precisely evaluate the fault kinematics and seismic hazard potential along this fault. Among these techniques, interferometric synthetic aperture radar (InSAR) stands out for its high spatial resolution and regular revisit intervals, enabling accurate mapping of interseismic deformation associated with fault motion. However, the precision of InSAR in measuring deformation encounters several challenges, particularly artifacts stemming from phase unwrapping errors and atmospheric phase delays. In this study, we utilize ascending and descending Sentinel-1 InSAR images spanning from January 2017 to January 2023 to drive the line-of-sight (LOS) mean crustal velocities associated with the XSHF with emphasis on phase unwrapping errors and atmospheric delay corrections. Then, the reliability of the derived LOS velocities is assessed using independent observations from the Global Navigation Satellite System (GNSS). The inferred fault slip rate along the XSHF shows significant along-strike variations, gradually decreasing from ~11.1 mm/yr at the Luhuo section to ~6.6 mm/yr at the Kangding section and then sharply increasing to ~13.0 mm/yr towards its eastern terminus at the Moxi section. The fault locking depth shows similar along-strike variations, decreasing from ~19.5 km in the northwestern part to ~4.8 km at the Kangding section, before increasing to 19.6 km at the Moxi segment. Notably, apparent surface fault creeping, characterized by a slip rate of ~2.7 mm/yr, is observed at the Kangding segment, likely resulting from postseismic slip following the 2014 Mw 6.3 Kangding earthquake. [ABSTRACT FROM AUTHOR]

The 2021 MW 7.4 Maduo event occurred within the Bayan Har block in eastern Tibet, which provides an opportunity to investigate the stress conditions and rheology of faults within the block. Here, we perform dynamic rupture simulations based on the finite element method to explore the physical conditions underlying this earthquake and the factors that controlled the rupture process. We construct the model with a nonplanar fault inferred from the Interferometric Synthetic Aperture Radar (InSAR) data and aftershocks sequence relocation. Our dynamic model is controlled by slip‐weakening friction law with initial stress on fault resolved from a uniform regional stress field. The preferred model produces an average slip of ∼2.2 m with a maximum slip of ∼4.0 m. There are three asperities distributed along the strike, which have captured the main features of the Maduo event. The simulation results are consistent with the static GPS coseismic surface displacements, InSAR data, and displacement waveforms recorded by high‐rate GNSS stations. By comparing the results with the planar fault model and rotated stress fields, we find that the fault geometry and regional stress field are the primary factors that control the rupture process of the event. Moreover, we infer that the unfavorable orientation and fault bend lead to minor slips on the branch fault. Furthermore, we investigate the potential mechanisms of supershear rupture on the eastern fault segment. Plain Language Summary: The 2021 Maduo event ruptured on an intra‐block fault of the Bayan Har block in the Tibetan Plateau, which has aroused widespread interest among the scientific community. In this study, we perform physics‐based numerical simulations based on a nonplanar fault to reproduce the source process of the event. The surface displacements obtained from our dynamic model are in good agreement with the observations. As the other parameters are relatively simple in our model, the source process of the event is mainly controlled by the geometric fault complexities. Our results also help to constrain the orientation of the regional stress field. We find that the branch fault of the earthquake is unfavorably oriented in the regional stress field as well as the fault bend also impedes the rupture to propagate on it, which leads to a minor slip on the branch fault. Furthermore, we infer that the supershear rupture may be induced by the free surface in the earthquake. Key Points: Our dynamic model reproduced the first‐order rupture characteristics of the Maduo earthquakeThe main factor that controls the multipeak slip pattern of the Maduo event is fault geometryThe orientation of the regional stress field was determined through numerical experiments [ABSTRACT FROM AUTHOR]

In recent decades, glaciers in the southeastern Tibetan Plateau (SETP) have been rapidly melting and showing a large scale of glacier mass loss. Due to the lack of large-scale, high-resolution, and high-precision observations, knowledge on the spatial distribution of the glacier mass balance and the response to climate change is limited in this region. We propose a TanDEM-X bi-static InSAR (Interferometric Synthetic Aperture Radar) algorithm with a non-local mean filter method and difference strategy, to improve the precision of glacier surface elevation change detection. Moreover, we improved the glacier mass balance estimation algorithm with a correction method for multi-source system errors and an uncertainty evaluation method based on error propagation theory to reduce the uncertainty of estimations. We used 13 pairs of TanDEM-X bi-static InSAR images to obtain the glacier mass balance data for the entire SETP. The total area of glaciers monitored was 5821 km2 and the total number of glaciers monitored was 2321; the glacier surface elevation change rate was −0.505 ± 0.005 m/yr, and the glacier mass balance estimation was −454.5 ± 13.1 mm w.eq. during 2000–2014. Additionally, we analyzed the spatial distribution of the glacier mass balance within the SETP using the sub-watershed analysis method. The results showed that the mass loss rate had a decreasing trend from the southeast to the northwest. Furthermore, the temperature change and the glacier mass loss rate showed a positive correlation from the southeast to the northwest in this region. This study greatly advances our understanding of the regularities of glacier dynamics in this region, and can provide scientific support for major national goals such as the rational utilization of surrounding water resources and construction of important transportation projects. [ABSTRACT FROM AUTHOR]

The Haiyuan fault system plays a crucial role in accommodating the eastward expansion of the Tibetan Plateau (TP) and is currently slipping at a rate of several centimeters per year. However, limited seismic activities have been observed using geodetic techniques in this area, impeding the comprehensive investigation into regional tectonics. In this study, the geometric structure and source models of the 2022 Mw 6.7 and the 2016 Mw 5.9 Menyuan earthquakes were investigated using Sentinel-1A SAR images. By implementing an atmospheric error correction method, the signal-to-noise ratio of the 2016 interferometric synthetic aperture radar (InSAR) coseismic deformation field was significantly improved, enabling InSAR observations with higher accuracy. The results showed that the reliability of the source models for those events was improved following the reduction in observation errors. The Coulomb stress resulting from the 2016 event may have promoted the strike-slip movement of the western segment of the Lenglongling fault zone, potentially expediting the occurrence of the 2022 earthquake. The coseismic slip distribution and the spatial distribution of aftershocks of the 2022 event suggested that the seismogenic fault may connect the western segment of the Lenglongling fault (LLLF) and the eastern segment of the Tuolaishan fault (TLSF). Additionally, the western segment of the surface rupture zone of the northern branch may terminate in the secondary branch close to the Sunan-Qilian fault (SN-QL) strike direction, and the earthquake may have triggered deep aftershocks and accelerated stress release within the deep seismogenic fault. [ABSTRACT FROM AUTHOR]

In the summertime, convective cells occur frequently over the Tibetan Plateau (TP) because of the large dynamic and thermal effects of the landmass. Measurements of vertical air velocity in convective cloud are useful for advancing our understanding of the dynamic and microphysical mechanisms of clouds and can be used to improve the parameterization of current numerical models. This paper presents a technique for retrieving high-resolution vertical air velocities in convective clouds over the TP through the use of Doppler spectra from vertically pointing Ka-band cloud radar. The method was based on the development of a "small-particle-traced" idea and its associated data processing, and it used three modes of radar. Spectral broadening corrections, uncertainty estimations, and results merging were used to ensure accurate results. Qualitative analysis of two typical convective cases showed that the retrievals were reliable and agreed with the expected results inferred from other radar measurements. A quantitative retrieval of vertical air motion from a ground-based optical disdrometer was used to compare with the radar-derived result. This comparison illustrated that, while the data trends from the two methods of retrieval were in agreement while identifying the updrafts and downdrafts, the cloud radar had a much higher resolution and was able to reveal the small-scale variations in vertical air motion. [ABSTRACT FROM AUTHOR]

In this study, The ENVISAT advanced synthetic aperture radar observations from 2003 to 2010 of a descending track covering an area of 100 km × 300 km were used to map the surface velocity field in northwestern Tibet. The derived line-of-sight (LOS) velocity map revealed that interseismic deformation was mainly located on the Altyn Tagh Fault (ATF) and other four immature subsidiary faults (i.e., Tashikule Fault, Muzitage-jingyuhe Fault, Heishibeihu Fault, and Woniuhu Fault). A 2D elastic screw dislocation model was used to interpret the interferometric synthetic aperture radar (InSAR) velocity profiles, which revealed the following results. (a) The oblique movement is partitioned between left-lateral slip at a rate of 6.3 ± 1.4 mm/y on the ATF and 5.9 ± 2.8 mm/y on the subsidiary faults. The low slip rate of the ATF indicates that the ATF does not drive the northeastward extrusion of material, with most of the extrusion occurring in the eastern interior of the plateau and the four subsidiary faults localizing the oblique convergence partitioned in the west. This can reasonably explain why catastrophic earthquakes and rapid slip do not occur all over along the ATF. (b) Based on the four subsidiary faults accommodating the oblique movement and the traces amalgamation with the EKLF (delineated Bayan Har plate boundary to the northeast), we concluded guardedly that the four subsidiary faults are the evoluting plate boundary of the Bayan Har block to the northwest. (c) The Tanan top-up structure had an uplift rate of ~0.6 mm/y at the south of the Tarim Basin. [ABSTRACT FROM AUTHOR]

The soil freeze-thaw (FT) state plays a significant role in cold ecosystems by influencing hydrology, geomorphology, ecology, thermodynamics, and soil chemistry. As climate change alters the frequency and timing of FT events, regions, such as the Tibetan Plateau and other subarctic permafrost zones, face significant environmental shifts, including land subsidence, altered hydrological processes, and carbon balance disturbances. This study aimed to detect frozen, thawed, and transition periods, with a particular emphasis on the identification of critical transition periods. A new approach called Percentile-based Freeze-Thaw Identification (PFTI) was applied to identify the three FT periodsusing C-band Synthetic Aperture Radar (SAR) data, specifically using Sentinel-1 VV and VH polarizations in both ascending and descending orbits. The PFTI approach is based on the Seasonal Threshold Approach (STA) with some modifications. We assessed the performance of PFTI against STA and validated it using the in-situ soil FT index. PFTI slightly improved the STA by 4% to 6% in detecting FT cycles over the Nagqu area of the Tibetan Plateau and Stordalen Mire in northern Sweden from 2017 to 2022. Moreover, PFTI demonstrated an accuracy of 94% without and 70% with transition periods in the Stordalen Mire, and 77% without and 50% with transition periods in the Nagqu area, as validated by in situ measurements. This study demonstrates the potential of PFTI on a monthly scale for detecting frozen, thawed, and transition periods on a regional scale to better monitor shifts due to the impacts of climate change in the most vulnerable regions. [ABSTRACT FROM AUTHOR]

The distribution and magnitude of forces driving lithospheric deformation in the India‐Eurasia collision zone have been debated over many decades. Here we test a two‐dimensional (2‐D) Thin Viscous Shell approach that has been adapted to explicitly account for displacement on major faults and investigate the impact of lateral variations in depth‐averaged lithospheric strength. We present a suite of dynamic models to explain the key features from new high‐resolution Sentinel‐1 Interferometric Synthetic Aperture Radar as well as Global Navigation Satellite System velocities. Comparisons between calculated and geodetically observed velocity and strain rate fields indicate: (a) internal buoyancy forces from Gravitational Potential Energy acting on a relatively weak region of highest topography (>2,000 m) contribute to dilatation of the high plateau and contraction on the margins; (b) a weak central Tibetan Plateau (∼1021 Pa s compared to far‐field depth‐averaged effective viscosity of at least 1022–1023 Pa s) is required to explain the observed long‐wavelength eastward velocity variation; (c) localized displacement on fault systems enables strain concentration and clockwise rotation around the Eastern Himalayan Syntaxis. We discuss the tectonic implications for rheology of the lithosphere, distribution of geodetic strain, and partitioning of active faulting and seismicity. Plain Language Summary: The collision of the Indian Plate with Eurasia has created the Tibetan Plateau, one of the largest deforming regions in the continents. The mode of deformation has been a focus for heated debate and has inspired two contrasting tectonic models: (a) The deformation is localized on major faults separating "blocks" or (b) the strain is distributed throughout a "continuum." We approximate the India‐Eurasia collision by treating the continent as a thin viscous shell with regional variations in strength, explicitly accounting for displacements on selected major faults. We present a suite of models to explain the key features of new geodetic measurements from satellites. The best‐fit model involves a weak Tibetan Plateau, a particularly weaker central plateau, and four strong regions outside the plateau, and allows displacements on major faults. This represents the deformation field of the India‐Eurasia collision zone as a combination of continuous distributed deformation and focused strain on major faults. Key Points: A suite of faulted viscous shell models testing key parameters explain new observations from geodesy for the India‐Asia collisionThe India‐Asia collision is explained by the balance between buoyancy and boundary forces, slip on faults, and internal strength variationsCentral Tibetan Plateau has a vertically‐averaged effective viscosity of ∼1021 Pa s, 1–2 orders lower than the surrounding area [ABSTRACT FROM AUTHOR]

The upstream Jinsha River, located in the eastern Tibetan Plateau, has been experiencing intense geological hazards characterized by a high density of ancient landslides, significant deformation and reactivation challenges. In this study, remote sensing interpretation, field investigations, and Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) technologies have been employed. Along a 17 km stretch of the Jinsha River, specifically in the Xiongba-Sela segment, 16 large-scale ancient landslides were identified, 9 of which are currently undergoing creeping deformation. Notably, the Sela and Xiongba ancient landslides exhibit significant deformation, with a maximum deformation rate of −192 mm/yr, indicating a high level of sliding activity. The volume of the Sela ancient landslide is estimated to be 1.8 × 108 to 4.5 × 108 m3, and characterized by extensive fissures and long-term creeping deformation. The SBAS-InSAR results revealed significant spatial variations in the deformation of the Sela ancient landslide, generally displaying two secondary zones of intense deformation, and landslide deformation exhibits nonlinear behavior with time. Between January 2016 and February 2022, Zone III1 on the southwest side of the Sela ancient landslide, experienced a maximum cumulative deformation of −857 mm, with a maximum deformation rate of −108 mm/yr. Zone III2, on the northeast side of the Sela ancient landslide, the maximum cumulative deformation was −456 mm, with a maximum deformation rate of −74 mm/yr; among these, the H2 and H4 secondary bodies on the south side of III1 are in the accelerative deformation stage and at the Warn warning level. We propose that the large-scale flood and debris flow disasters triggered by the Baige landslide-dammed lake-dam broken disaster chain in Tibetan Plateau during October and November 2018 caused severe erosion at the foot of downstream slopes. This far-field triggering effect accelerated the creep of the downstream ancient landslides. Consequently, the deformation rate of Zone III2 of the Sela ancient landslide increased by 6 to 8 times, exhibiting traction-type style reactivation. This heightened activity raises concerns about the potential for large-scale or overall reactivation of the landslide, posing a risk of damming the Jinsha River and initiating a dam-break disaster chain. Our research on the reactivation characteristics and mechanisms of large ancient landslides in high deep-cut valleys provides valuable guidance for geological hazard investigation and risk prevention. [ABSTRACT FROM AUTHOR]

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Constraining the lithospheric rheology of Tibetan Plateau is important for the physical understanding of its tectonics. Siling Co, the largest high‐altitude lake in the world, has experienced a rapid water level increase in the 2000s. The resulting loading changes stimulate the viscoelastic response of the lower crust, giving access to study the lithospheric rheology in central Tibet. Here, we derive a clear subsidence signal around the lake with peak velocity of 4 mm/yr from two tracks of Sentinel‐1 InSAR images acquired from 2017 to 2022. Our viscoelastic modeling suggests a ductile layer 15 km beneath the surface with a decadal‐scale, steady‐state viscosity of 1–4 × 1019 Pa s. This value is consistent with the viscosity inferred from millennium‐scale shoreline changes, but is about 10 times higher than the viscosities derived from the deformation surrounding Siling Co before 2011, highlighting the role of transient viscosity in controlling the surface deformation. Plain Language Summary: The change of surface loading will cause the response of earth lithosphere, including instantaneous, concentrated elastic and delayed, wide‐range viscoelastic deformation at the surface. With the change of climate, the amount of water in many lakes in the Tibetan Plateau has changed. The resulted water loading changes can cause surface deformation that can be measured by space‐borne radar images. Using the Interferometric Synthetic Aperture Radar (InSAR), we measure the deformation around the Siling Co, the largest high‐altitude lake in the world, with the peak subsidence velocity of up to 4 mm/yr. According to numerical modeling, we find that the deformation mainly comes from the viscoelastic response of the ductile layer 15 km beneath the surface. The inferred viscosity of 1–4 × 1019 Pa s is consistent with the value derived from millennium‐scale shoreline changes. Our research links the surface displacement with the strengths of the deep earth, providing a direct constraint for geodynamics models. Key Points: We observe subsidence around the Siling Co from Sentinel‐1 InSAR images acquired between 2017 and 2022 with a peak rate of 4 mm/yrA ductile layer below 15 km with a viscosity of 1–4 × 1019 Pa s can explain the observed subsidence around the Siling CoThis decadal‐scale viscosity is consistent with the millennial‐scale value derived from paleoshoreline changes around the Siling Co [ABSTRACT FROM AUTHOR]

The Tibetan Plateau stands as one of China's largest middle and low latitude permafrost regions. However, the effects of global warming and human activities have led to permafrost thawing, inducing surface instability and posing significant threats to infrastructure and indigenous communities. The deployment of Lu Tan-1 (LT-1), China's premier L-band synthetic aperture radar (SAR) satellite constellation, offers a novel opportunity to assess these changes. This paper evaluates the deformation of critical engineering corridors, such as the Qinghai-Tibet Railway (QTR) and the Qinghai-Tibet Highway (QTH), utilizing time-series InSAR techniques with LT-1 SAR constellation data. We introduce both Stacking InSAR and a multi-baseline persistent scatterer multitemporal (MT-InSAR) method to enhance permafrost and engineering corridor deformation detection capabilities. Results obtained through the MT-InSAR approach reveal line-of-sight (LOS) deformation velocities of permafrost in the Beiluhe region ranging from -90 mm/y to approximately 70 mm/y, with an average velocity amplitude of 0.06 m/y. Differential displacement between alpine meadows and alpine deserts across the Beiluhe region is successfully discerned using LT-1 SAR data. Deformation velocities of QTR, QTH were found to be lower than that of permafrost, with average velocities of 0.027 m/y. These findings underscore the LT-1 SAR constellation's potential to serve as a valuable SAR data source for monitoring engineering corridor deformation within the Tibetan Plateau permafrost region. [ABSTRACT FROM AUTHOR]

Investigating the response of landslide activity to climate change is crucial for understanding the disastrous effects of climate change on high mountains. However, the lack of long-term, spatial-temporal consistent measurement of landslide activity prohibits the study of this relationship. In this work, we used two methods to derive the time series of a landslide's deformation and study its relationship with precipitation in the northeastern Tibetan Plateau. The small baseline subset-interferometric synthetic aperture radar (SBAS-InSAR) method with Sentinel-1A images is first applied to derive time series of the landslide's deformation from 2020 to 2021. A recently developed method to derive cumulative deformations of optical images was used with Landsat 5 and Sentinel-2 images to derive the long-term deformation time series from 1986 to 2023. Centimeter-scale deformations detected by using the InSAR method are mainly located in the upper and eastern parts of the landslide, whereas meter-scale deformations detected by using the optical method are in the middle of the landslide. Time-series results from both methods show that intra-annual initiations of the landslide's deformation occurred in rainy months (from July to October). Although there seems to be no direct relations between inter-annual deformations and precipitation, significant displacements since 2020 occurred after exceptionally wet years from 2018 (with a record-breaking precipitation year in 2020). With optical images, we found that the maximum cumulative deformation of the landslide has been >35 m since 1986 with major deformations (>20 m) found after 2020, which may indicate an imminent risk to the Lijie town near the toe of the landslide. With climate change, increased precipitation is expected in future, which may trigger more similar landslides in the vicinity of this region. This work demonstrates an executable framework to assess landslide hazard risk under climate change. [ABSTRACT FROM AUTHOR]

The summer season raindrop size distribution (DSD) characteristics and their important applications, based on a PARSIVEL2 disdrometer installed in Zhaosu over the western Tianshan Mountains, China, in 2020–2021 are studied. Our analysis reveals that, for total rainfall and different rainfall types, the DSD in Zhaosu follows the normalized gamma distribution model, and convective rainfall has a higher raindrop concentration than stratiform rainfall at all diameters. For stratiform rainfall, the mean value of mass-weighted mean diameter (Dm) is lower than that of convective DSD, while the mean value of normalized intercept parameter (log10 Nw) is higher than that of convective DSD, and the summer season convective rainfall in Zhaosu is continental convective rainfall according to the conventional classification, which is characterized by relatively larger Dm and lower log10 Nw values. The derived µ–∧ relation in Zhaosu exhibits some differences from those reported in eastern, southern, and northern China and the Tibetan Plateau. Furthermore, derived Z–R relations for stratiform and convective rainfall in Zhaosu are compared with those from other regions. Analysis shows that the empirical relation of Z = 300R1.4 (widely used), strongly overestimates the R of convective precipitation in Zhaosu. The C-band polarimetric radar rainfall estimation relations are derived, and the R(Zh,Zdr) and R(Kdp,Zdr) relations perform the best in quantitative precipitation estimation. Moreover, the empirical Dm–Zku and Dm–Zka relations are derived, which are beneficial to the improvement of rainfall retrieval algorithms of the GPM DPR. Lastly, rainfall kinetic energy relations proposed in this study can be used to better assess rainfall erosivity. The empirical relationships of DSD evaluated in this study provide an opportunity to (1) improve rainfall retrieval algorithms for both ground-based and remote sensing radars and to (2) enhance rainfall kinetic energy estimates in rainfall erosivity studies based on disdrometer and GPM DPR. [ABSTRACT FROM AUTHOR]

The snow penetration depth is a necessary input parameter to accurately evaluate the thickness and vertical structure of snow layer, which is conducive to understanding the freeze-thaw process of ice and snow and predicting the change of ice and snow mass balance. Interferometric Synthetic Aperture Radar (InSAR) exhibits great potential in estimating snow penetration depth due to the emission of microwave band and the ability of operating under all-day and all-weather conditions. In previous studies, the penetration depth of snow was obtained based on InSAR coherence, but the external factors such as temperature, humidity, topography, dielectric constant and so on also affect the penetration dept. In order to extract the penetration depth in detail, this paper this paper adopts a uniform volume model as the basis, introduces two parameters describing the physical properties of snow: the volume ambiguity height and the volumetric decorrelation. Then, the magnitude of volumetric decorrelation is used to establish the internal relationship between the magnitude and the volume ambiguity height to estimate the snow penetration depth. In order to verify the effectiveness and feasibility of this method, a TSX/TDX InSAR pair covering southeast Tibetan Plateau in 2012 is applied to estimate the snow penetration depth. And results indicate that X-band penetration depths range mainly between −2.753 meters and −4.589 meters with an average value of −3.671 meters m and standard deviation of 0.918 meters in snowy regions on the plateau. [ABSTRACT FROM AUTHOR]

This study examines the Zhama ancient landslide, one of several large-scale ancient landslides with complex formation mechanisms and significant reactivation trends found in the Batang Fault zone of the eastern Tibetan Plateau. The Zhama landslide, located in Deda Township, Batang County, Sichuan Province, has a dustpan shape with dimensions of 1750 m in length, 710 m in width, and a height difference of 1000 m. Based on unmanned aerial vehicle light detection and ranging (UAV LiDAR), small baseline subset interferometric synthetic aperture radar (SBAS-InSAR), optical remote sensing interpretation, field investigation, geophysical prospecting, and drilling, the study identifies two-level sliding zones, which were found at 31.4–33.4 m and 77.7–81 m in drill hole ZK1 and at 46.6–47.6 m and 80.4–93.8 m in drill hole ZK2. The volume of the landslide is estimated to be approximately 2.5 × 107–3.1 × 107 m3. The Zhama landslide is divided into the landslide zone of depletion (I) and the landslide zone of accumulation (II), which can be further divided into the central local stability zone (II1) and the foot edge strong deformation zone (II2, II3). The surface deformation rate of the strong deformation zone (II2) at the foot edge of the Zhama ancient landslide is approximately − 65.8 mm/a. The reactivation of the landslide is influenced by heavy rainfall, earthquakes, fault activities, river erosion, and loading on the head edge of the landslide. Numerical simulations suggest that under heavy rain and seismic activities conditions, the head edge of the landslide deforms greatly, causing the middle and front slope to push and form a push-type landslide. Overall, this study sheds light on the development characteristics and reactivation mechanism of the Zhama ancient landslide, providing valuable insights into the hazards posed by large-scale ancient landslides in the Batang Fault zone. [ABSTRACT FROM AUTHOR]

In recent years, numerous ancient landslides initially triggered by historic earthquakes on the eastern Tibetan Plateau have been reactivated by fault activity and heavy rainfall, causing severe human and economic losses. Previous studies have indicated that short-term heavy rainfall plays a crucial role in the reactivation of ancient landslides. However, the deformation behavior and reactivation mechanisms of seasonal rainfall-induced ancient landslides remain poorly understood. In this paper, taking the Dandu ancient landslide as an example, field investigations, ring shear experiments, and interferometric synthetic aperture radar (InSAR) deformation monitoring were performed. The cracks in the landslide, formed by fault creeping and seismic activity, provide pathways for rainwater infiltration, ultimately reducing the shear resistance of the slip zone and causing reactivation and deformation of the Dandu landslide. The deformation behavior of landslides is very responsive to seasonal rainfall, with sliding movements beginning to accelerate sharply during the rainy season and decelerating during the dry season. However, this response generally lags by several weeks, indicating that rainfall takes time to infiltrate into the slip zone. These research results could help us better understand the reactivation mechanism of ancient landslides triggered by seasonal rainfall. Furthermore, these findings explain why many slope failures take place in the dry season, which typically occurs approximately a month after the rainy season, rather than in the rainy season itself. [ABSTRACT FROM AUTHOR]

Although geomorphic evidence and shallow geometry of active faults are significant for the understanding and assessing of fault activity and seismic hazards, it is challenging to acquire high-resolution topographic data and shallow geometry of the Yushu fault by conventional methods. Here, we present a case study to reconstruct the detailed surficial and subsurface geometry of the Yushu fault using terrestrial laser scanning (TLS), multi-frequency ground penetrating radar (GPR) and trenching. TLS was suitable for measuring the high-resolution three-dimensional (3D) topographic data of the fault. GPR surveys with different frequency antennas (25 MHz, 100 MHz, 250 MHz and 500 MHz) were conducted to image the shallow geometry of active faults at different depths and spatial resolutions. The typical groove landscape, parallel to surface traces of the fault, was clearly observed on the TLS-derived data. A ~40 m width narrow fault system and three faults were identified on the different frequency GPR profiles. Furthermore, faults F1 and F2 were supposed to be boundary faults but were sinistral-lateral strike-slip faults with a normal component, while fault F3 was inferred as the secondary fault. The western trench section, despite the limited investigation depth (~2 m), was well consistent with the 500 MHz GPR result, especially in the location of fault F2. Finally, a 3D surficial and subsurface model was established from the TLS-derived data and GPR data offering multi-sensor and multi-view spatial data to characterize and understand the fault's kinematics and characteristics. In addition, the shallow geometry of the fault on the GPR results would be better interpreted with the help of the corresponding surficial data. The study results demonstrate that a combination of TLS, multi-frequency GPRs and trenching can be successfully used for reconstructing a detailed surficial and subsurface geometry of the Yushu fault. It will play an increasing role in comprehensive understanding and assessing fault behavior and seismic hazards, especially on the Tibetan Plateau and the adjacent area. [ABSTRACT FROM AUTHOR]

This study investigates the characteristics of mesoscale convective systems (MCSs) as a function of MCS organizational mode over China, using long-term precipitation radar observations from the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement Mission (GPM). The spaceborne radar-based MCS climatology shows maximum population over low-elevation regions, marked decrease over the foothills, and minimum frequency over the Tibetan Plateau. Linear and nonlinear MCSs account for 17% and 83% of the MCSs over China, respectively. Linear MCSs have much stronger convective intensity and heavier precipitation than nonlinear MCSs, as indicated by TRMM convective proxies. Interestingly, though broad-stratiform MCSs have the weakest convection, they produce the heaviest (maximum) rain rate and the largest amount of heavy rainfall among nonlinear MCSs. Among various types of linear MCSs, bow echoes (BEs) and no-stratiform (NS) systems exhibit the strongest convective intensity, embedded lines exhibit the weakest, and convective lines with trailing/leading stratiform in between. BEs and NSs share the most vertically extended structure, strongest microwave ice scattering, and highest lightning flash rates, but NS systems have a much lower surface rain rate likely due to a drier environment. Vertical radar reflectivity profiles suggest that both ice-based and warm-rain processes play an important role in the precipitation processes of linear MCSs over China, including the most intense BE storms. In short, this study helps to better understand the convective organization, precipitation structure, and ensemble microphysical properties of MCSs over China, and potentially provides guidelines for evaluating high-resolution model simulations and satellite rainfall retrievals for monsoonal MCSs. [ABSTRACT FROM AUTHOR]

Interferometric synthetic aperture radar (InSAR) can monitor large-scale small deformation. Because the Sentinel-1 satellite has a stable orbit control and the data coherence in Qinghai–Tibet Plateau is good, we utilize data from Sentinel-1 to analyze the slip deformation of the Gyaring Co fault (GCF) in the central Tibetan Plateau. Data are obtained from ascending and descending tracks covering the research area, and the deformation results are obtained by the stacking and analysis of time series. The results demonstrate that the GCF exhibit slow slip overall. An analysis of different sections indicates that the fault displays both right-lateral strike-slip and normal faulting behaviors, and the movement is particularly obvious in the middle section of the GCF. Furthermore, we investigate the contemporary slip rate of the GCF using GPS data and construct two velocity profiles perpendicular to the fault strike at the southeastern and northwestern ends of the fault. The southeastern profile shows ~ 4 mm/year of right-lateral strike-slip movement and a modest (< 1 mm/year) amount of crustal thickening across the fault, while the northwestern profile shows much slower (~ 1 mm/year) right-lateral strike-slip motion and 0.5 mm/year of crustal extension. The GPS results are consistent with the InSAR deformation map derived using Sentinel-1 A/B data from 2014 to 2017. Our results support the distributed crustal motion model in which most crustal deformation (shortening/extension/strike-slip) occurs on various active faults in the central Tibetan Plateau rather than being concentrated on several fast-moving fault zones, e.g., the GCF-BCF. Finally, we analyze the distribution of historical earthquakes and the gravity and aeromagnetic fields. We speculate that a fault may exist north of Gyaring Co Lake that may be an extension of the fault north of Mujiu Co Lake. [ABSTRACT FROM AUTHOR]

Abstract: We used 50-MHz ground-penetrating radar to detect the boundary of permafrost in Xidatan region, the northern limit of the marginal and sporadic permafrost area on the Tibetan Plateau, China. We interpreted the lower limit of permafrost from nine radar profiles to determine the boundary between the permafrost and non-permafrost region. We also sketched the locations of permafrost table along the nine profiles and acquired the lower alpine limit of permafrost in this area. Based on the lower alpine limit of permafrost determined in this field survey, a new permafrost distribution map was drawn with the help of GIS analyses. Comparing with the research work in 1975, permafrost in Xidatan is reduced 12% in area and the lower alpine limit has increased by 25 m. The situation of global warming, apparent climatic warming recorded at two stations near Xidatan, could be responsible for permafrost degradation in this area. [Copyright &y& Elsevier]

Employing a small baseline subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) and hotspot analysis, this study identified 81 potential landslides in a 768.7 km2 area of Xiaojin county, eastern Tibetan Plateau. Subsequent time-series deformation analysis revealed that these potential landslides are in the secondary creep stage. The newly identified landslides were compared to a landslide inventory (LI), established through field surveying, in terms of causative factors, including altitude, slope, relief amplitude, distance to river, distance to road, and slope curvature. From the comparison, the InSAR technique showed the following advantages: (1) it identified 25 potential landslides at high altitudes (>3415 m) in addition to the low-altitude landslides identified through the field survey. (2) It obtained approximately 37.5% and 70% increases in the number of potential landslides in the slope angle ranges of 20°–30° and 30°–40°, respectively. (3) It revealed significant increases in potential landslides in every relief amplitude bin, especially in the range from 58 m to 92 m. (4) It can highlight key geological factors controlling landslides, i.e., the stratigraphic occurrence and key joints as the InSAR technique is a powerful tool for identifying landslides in all dip directions. (5) It reveals the dominant failure modes, such as sliding along the soil–rock interface and/or interfaces formed by complicated combinations of discontinuities. This work presents the significant potential of InSAR techniques in gaining deeper knowledge on landslide development in alpine forest regions. [ABSTRACT FROM AUTHOR]

The 1,000 km‐long Haiyuan fault is the largest strike‐slip fault system in the northeastern Tibetan Plateau, accommodating part of the plateau's eastward extrusion. However, few large earthquakes have been instrumentally recorded, hindering our understanding of strain partitioning across the fault system. Here, we use synthetic aperture radar images to investigate fault geometries and slip distributions of the adjacent 2016 Mw5.9 and 2022 Mw6.7 Menyuan earthquakes that occurred 35 km apart along the western Haiyuan fault system. The purely strike and purely thrust slips of the 2022 and 2016 events indicate that strain was released separately on shallow steep fault and low‐angle fault at depth. We propose that such strain partitioning is controlled by the ratio between interseismic shear and normal velocities and the branching fault structure beneath the Lenglongling segment. Seismic hazard due to both focal mechanisms has to be considered along the western Haiyuan fault in northeastern Tibet. Plain Language Summary: Apart by 35 km, two earthquakes occurred on 20 January 2016 and 7 January 2022 with the moment magnitude of Mw5.9 and Mw6.7 along the western Haiyuan fault system, near Menyuan county, China. They are the largest events on the Lenglongling (LLL) mountain in past decades and also the only ones with clear surface deformation captured by radar imaging geodesy. Here, we use Synthetic aperture radar images to measure the surface deformations caused by these two events and derive their fault geometries and slip distributions. For the 2022 event, our modeling shows that the rupture propagated on both the LLL and the Tuolaishan (TLS) fault, supporting that the Haiyuan fault system may extend westward through LLL to the TLS fault. The purely thrust‐slip and purely strike‐slip mechanisms of the 2016 and 2022 events indicate the strain partitioning that the shear and normal strain can be released by the strike‐slip event and thrust event separately. Such strain partitioning reminds us to consider seismic hazards due to both shallow strike‐slip and deep thrust earthquakes along the western Haiyuan fault system. Key Points: Slip distributions of the 2016 Mw5.9 and 2022 Mw6.7 Menyuan earthquakes are derived from Sentinel‐1 interferograms and pixel offsetsThe 2022 Menyuan earthquake suggests the Tuolaishan fault may as the continuation of the Haiyuan fault west of the Lenglongling faultCoseismic slip partitioning along the western Haiyuan fault agrees with the interseismic shear‐to‐normal strain ratio and fault geometries [ABSTRACT FROM AUTHOR]

The launches of the Sentinel‐1 synthetic aperture radar satellites in 2014 and 2016 started a new era of high‐resolution velocity and strain rate mapping for the continents. However, multiple challenges exist in tying independently processed velocity data sets to a common reference frame and producing high‐resolution strain rate fields. We analyze Sentinel‐1 data acquired between 2014 and 2019 over the northeast Tibetan Plateau, and develop new methods to derive east and vertical velocities with ∼100 m resolution and ∼1 mm/yr accuracy across an area of 440,000 km2. By implementing a new method of combining horizontal gradients of filtered east and interpolated north velocities, we derive the first ∼1 km resolution strain rate field for this tectonically active region. The strain rate fields show concentrated shear strain along the Haiyuan and East Kunlun Faults, and local contractional strain on fault junctions, within the Qilianshan thrusts, and around the Longyangxia Reservoir. The Laohushan‐Jingtai creeping section of the Haiyuan Fault is highlighted in our data set by extremely rapid strain rates. Strain across unknown portions of the Haiyuan Fault system, including shear on the eastern extension of the Dabanshan Fault and contraction at the western flank of the Quwushan, highlight unmapped tectonic structures. In addition to the uplift across most of the lowlands, the vertical velocities also contain climatic, hydrological or anthropogenic‐related deformation signals. We demonstrate the enhanced view of large‐scale active tectonic processes provided by high‐resolution velocities and strain rates derived from Sentinel‐1 data and highlight associated wide‐ranging research applications. Plain Language Summary: The new‐generation radar satellites permit the derivation of crustal velocities in fine resolution over continental scales. With the technical advancements developed in this study, we reveal unseen details of the crustal deformation over the earthquake‐prone Hexi Corridor in the northeast corner of the Tibetan Plateau. In particular, we observe concentrated elastic loading along, and at branch points of, major earthquake‐generating faults. The ability to monitor such phenomena is important for understanding future seismic hazard as such geometrical complexities along faults are often associated with earthquake triggering and termination. We also draw attention to previously unknown structures that are rapidly deforming. This new and enhanced view of the local tectonic setting could improve local seismic hazard assessment. Last but not least, we observe climatic, hydrological and anthropogenic signals in the vertical velocity field, which are related to permafrost thawing, blocked river drainage, mining, damming and the extraction of groundwater for farming. Overall, we demonstrate the wealth of information that can be derived from the rapidly growing space‐born Earth observation data, which are destined to play an important role in shaping a more resilient world for the future. Key Points: We present new methods to mosaic line‐of‐sight velocity frames, derive Cartesian velocities, and produce high‐resolution strain‐rate mapsWe construct 440,000 km2 maps of east‐west, vertical velocities, and strain rates over NE Tibet from Sentinel‐1 interferometryWe quantify strain partitioning, measure creep rate, identify unmapped structures and climatic, hydrological and anthropogenic signals [ABSTRACT FROM AUTHOR]

Recent geodetic observations of shallow fault creep have illuminated increasingly complex, time-dependent slip behaviors, including quasi-steady creep and temporary accelerations, termed slow-slip events. We documented two decades of deformation on the Xidatan fault on the Tibetan Plateau measured by radar interferometry during 2003-2010 and 2015-2020 CE, to probe the temporal evolution of shallow creep and illuminate the underlying mechanisms. The geodetic observations reveal an -80-km-long fault section with temporally decaying creep along the Xidatan fault, one of the current seismic gaps along the Kunlun fault. The transient creep is likely driven by postseismic deformation processes, dominated by viscoelastic relaxation after the 2001 Kokoxili earthquake, rather than triggered by the coseismic rupture. The transient creep behavior, indicating rate-strengthening frictional properties of the fault, contradicts the inference of locking along the Xidatan fault, based on geodetic imaging before the Kokoxili earthquake and on historical ruptures. We propose that, during the interseismic period, the frictionally unlocked shallow portions of the fault are located in the stress shadow cast by the deeper locked asperities, but they creep at resolvable rates when exposed to transient stress and stressing rate increases. We argue that stress interactions in the triple junction of the Kusai Hu, Xidatan, and Kunlun Pass faults promote complex slip behaviors throughout the earthquake cycle. [ABSTRACT FROM AUTHOR]

The Nyainrong microcontinent carries key information about the ongoing evolution of the central Tibetan Plateau. The 2021 Mw 5.7 Nagqu earthquake is the largest instrumentally recorded event inside this microcontinent, which provides an ideal opportunity to elucidate the influence of this ancient microcontinent on the seismogenic mechanisms, stress heterogeneity and strain partitioning across the Tibetan Plateau. Here, we constrain the seismogenic fault geometry and distributed fault slip using Interferometric Synthetic Aperture Radar (InSAR) observations. By using the regional focal mechanism solutions, we invert the stress regimes surrounding the Nyainrong microcontinent. Our analysis demonstrates that the mainshock was caused by a normal fault with a comparable sinistral strike-slip component on a North-West dipping fault plane. The Nyainrong microcontinent is surrounded by a dominant normal faulting stress regime to the northeast and a dominant strike-slip stress regime to the southwest. Moreover, the clockwise rotation of the maximum horizontal stress (SHmax) from the southwest to the northeast is ~20°. This indicates that the Nyainrong microcontinent is involved in the mainshock occurrence as well as regional stress heterogeneity, and strain partitioning. Our results highlight the significance of the ancient microcontinent in the tectonic evolution of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Selin Co, located within permafrost regions surrounded by glaciers, has exhibited the greatest increase in water storage among all the lakes on the Tibetan Plateau over the last 50 years. Most of the increased lake water volume has been attributed to increased precipitation and the accelerated melting of glacier ice, but these processes are still not sufficient to close the water budget with the expansion of Selin Co. Ground ice meltwater released by thawing permafrost due to continuous climate warming over the past several decades is regarded as another source of lake expansion. This study presents the first attempt to quantify the water contribution of ground ice melting to the expansion of Selin Co by evaluating the ground surface deformation. We monitored the spatial distribution of surface deformation in the Selin Co basin using the small baseline subset (SBAS) interferometric synthetic aperture radar (InSAR) technique and compared the results with the findings of field surveys. Then, the ground ice meltwater volume in the watershed was calculated based on the cumulated settlement. Finally, this volume was compared with the lake volume change during the same period, and the contribution ratio was derived. SBAS-InSAR monitoring during 2017–2020 illustrated widespread and large subsidence in the upstream section of the Zhajiazangbu subbasin, where widespread continuous permafrost is present. The terrain subsidence rate was normally between 5 and 20 mm a -1 , indicating rapid ground ice loss in the region. The ground ice meltwater was released at a rate of ∼57×106 m 3 a -1 , and the rate of increase in lake water storage was ∼485×106 m 3 a -1 during the same period, with ground ice meltwater contributing ∼12 % of the lake volume increase. This study contributes to explaining the rapid expansion of Selin Co and equilibrating the water balance at the watershed scale. More importantly, the proposed method can be extended to other watersheds underlain by permafrost and help in understanding the hydrological changes in these watersheds. [ABSTRACT FROM AUTHOR]

We use Sentinel‐1 and ALOS‐2 Interferometric Synthetic Aperture Radar (InSAR), and Global Navigation Satellite System (GNSS) data to investigate the mechanisms of coseismic and postseismic deformation due to the 2021 M7.4 Maduo (China) earthquake. We present a refined coseismic slip model constrained by the rupture trace and precisely located aftershocks. The InSAR time series corrected for the atmospheric and decorrelation noise reveal postseismic line of sight displacements up to ∼0.1 m. The displacements are discontinuous along the fault trace, indicating shallow afterslip and velocity‐strengthening friction in the top 2–3 km of the upper crust. The magnitude of shallow afterslip is however insufficient to compensate for the coseismic slip deficit, implying substantial off‐fault yielding. The observed surface deformation does not exhibit obvious features that could be attributed to poroelastic effects. We developed a fully coupled model that accounts for both stress‐driven creep on a deep localized shear zone and viscoelastic relaxation in the bulk of the lower crust. The mid‐ to near‐field data can be reasonably well explained by deep afterslip and/or non‐Maxwellian visco‐elasticity. Our results suggest a power‐law stress exponent of ∼4–4.5 assuming a power‐law rheology, and transient and steady‐state viscosities of 1018 and 1019 Pa s, respectively, assuming a bi‐viscous (Burgers) rheology. However, a good fit to the GNSS data cannot be achieved assuming the bulk viscoelastic relaxation alone, and requires a contribution of deep afterlip and/or a localized shear zone extending through much of the lower crust. Plain Language Summary: A large earthquake occurred in the north‐east Tibetan Plateau (Qinghai Province, China) on 21 May 2021. We use data collected by orbiting satellites to measure subtle (millimeter to centimeter‐scale) displacements of the Earth's surface that occurred in 1 year following the Maduo earthquake. The observed rates and spatial patterns of surface displacements are used to infer the mechanisms of stress relaxation and mechanical properties of rocks at depth. We find evidence of continued slip on the fault that produced the Maduo earthquake, both near the surface, and below the seismogenic zone. Our results suggest that major faults that cut through the Tibetan Plateau are associated with deep roots that extend into the lower crust. The observed shallow slip is insufficient to compensate for the near‐surface slip deficit that accrued during the earthquake. This suggests that some amount of the near‐surface coseismic shear was distributed over a wider zone around the earthquake rupture. Key Points: We present a new method for modeling geometrically complex ruptures in heterogeneous media using distributed point sourcesPostseismic deformation is best explained by models that include a deep shear zone below the earthquake ruptureUp to ∼0.2 m of shallow afterslip occurred within 1 year after the earthquake, insufficient to compensate for the coseismic shallow slip deficit [ABSTRACT FROM AUTHOR]

The ground deformation rate is an important index for evaluating the stability and degradation of permafrost. Due to limited accessibility, in-situ measurement of the ground deformation of permafrost areas on the Tibetan Plateau is a challenge. Thus, the technique of time-series interferometric synthetic aperture radar (InSAR) is often adopted for measuring the ground deformation rate of the permafrost area, the effectiveness of which is, however, degraded in areas with geometric distortions in synthetic aperture radar (SAR) images. In this study, a method that integrates InSAR and the random forest method is proposed for an improved permafrost stability mapping on the Tibetan Plateau; to demonstrate the application of the proposed method, the permafrost stability mapping in a small area located in the central region of the Tibetan Plateau is studied. First, the ground deformation rate in the concerned area is studied with InSAR, in which 67 Sentinel-1 scenes taken in the period from 2014 to 2020 are collected and analyzed. Second, the relationship between the environmental factors (i.e., topography, land cover, land surface temperature, and distance to road) and the permafrost stability is mapped with the random forest method based on the high-quality data extracted from the initial InSAR analysis. Third, the permafrost stability in the whole study area is mapped with the trained random forest model, and the issue of data scarcity in areas where the terrain visibility of SAR images is poor or InSAR results are not available in permafrost stability mapping can be overcome. Comparative analyses demonstrate that the integration of the InSAR and the random forest method yields a more effective permafrost stability mapping compared with the sole application of InSAR analysis. [ABSTRACT FROM AUTHOR]

This paper presents the first measurement of multi-decadal thickness and volume changes (1969–2000) of the Dongkemadi Ice Field (DIF) in the Tanggula Mountains, central Qinghai-Tibetan Plateau, China, using multi-source remote sensing data. These include the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) acquired in February, 2000, a DEM generated by digitising analogue topographic maps from 1969, and Landsat ETM+ imagery from 2000. Digital glacier outlines and GIS-based processing were used to calculate an elevation difference map to evaluate the relative elevation error of these two DEMs over ice-free areas. This method was also used to identify regions of glacier elevation thinning and thickening corresponding to glacier mass loss and gain. Analysis of 67,520 points on flat grass and rock terrain surrounding the DIF, with a slope less than 25°, showed a mean elevation difference of –0.90 m and a standard deviation of 5.58 m. A thickness change error within ±6 m was estimated. Between 1969 and 2000, 76.51% of the whole DIF area appeared to be thinning while 23.49% showed thickening. The average glacier surface thinning was –12.58 m with a standard deviation of 18.29 m and the estimated volume loss was 1.17 km3. The standard deviation of volume change was 0.0006 km3 over the DIF. A thinning rate up to 0.41±0.194 m a−1 or 0.038 km3 a−1 for the volume loss was observed for the whole ice field, which seems to be evidence for the ongoing retreat of glaciers on the Qinghai-Tibetan Plateau. It was found that the spatial thickness change pattern derived from the remote sensing method was consistent with the thickness change results of the Small Dongkemadi Glacier (SDG) from field measurements. The estimated error of the annual thickness change rate was on the order of 5%. The relationship between elevation change and absolute glacier elevation over typical glaciers was also analysed, showing considerable variability. These changes have possibly resulted from increased temperature and decreased precipitation in this region. [ABSTRACT FROM AUTHOR]

The Sichuan earthquake, Mw 7.9, struck the Longmen Shan (LMS) range front, China, on 2008 May 12, affecting an area of moderate historical seismicity where little active shortening has been previously reported. Recent studies based on space geodesy have succeeded in retrieving the far field surface displacements caused by the earthquake, but the near field (±25 km from the faults) coseismic surface displacement is still poorly constrained. Thus, shallow fault geometry and shallow coseismic slip are still poorly resolved. Here, for the first time for this earthquake, we combine C and L-band Synthetic Aperture Radar offsets data from ascending and descending tracks to invert for the 3-D surface displacement in the near coseismic field of the Sichuan earthquake. Our data, coupled with a simple elastic dislocation model, provide new results strongly suggesting the presence of a blind thrust striking along the range front and being active at depth during the earthquake. The presence of a rupture on a blind thrust brings new evidence for an out-of-sequence thrusting event and new elements for interpreting the tectonic strain partitioning in the LMS, which has important implications both for seismic hazard assessment and long-term evolution of the mountain belt. [ABSTRACT FROM AUTHOR]

The article presents a study on the application of multi-channel ground-penetrating radar (GPR) at a permafrost site in the Tibetan Plateau to explore spatial variations in thaw depth and moisture content in the active layer in China. Measurements were conducted on an area with surface bare soil to finer textured, thinly vegetated areas covered with fine and wind blown gravel road. The study shows the complicated interactions between surface and subsurface state variables in this environment.

The southeastern Tibetan Plateau (TP) is the critical region of water vapor transport over the TP. Ground-based Ka-band cloud radar (KaCR) measurements collected at the Motuo National Climate Observatory in 2019 were used to analyze the physical properties of clouds at the front of the water vapor channel over the TP. The cloud top heights (CTHs) measured by the KaCR were verified through a comparison with observations from the Fengyun-4A (FY-4A) satellite at the same location. The KaCR-obtained CTHs were generally consistent with the FY-4A-obtained CTHs, although the KaCR slightly overestimated the CTHs of nonprecipitation clouds and underestimated the CTHs of precipitation clouds. Negative deviations between the KaCR- and FY-4A-obtained CTHs increased with rainfall rate. Cloud cover frequently occurred over Motuo, with an annual mean occurrence frequency of 65.3%. Clouds tended to form frequently at night and dissipate gradually in the daytime. Two peaks in the cloud base height (CBH) distribution were observed in Motuo, located at 0–1 km and 2–3 km, corresponding to precipitation and nonprecipitation clouds, respectively. The CTHs reached a peak at 6–7 km, which might be related to precipitation clouds. Moreover, a maximum CTH probability was observed in the midnight-early morning hours during the rainy season, while the CTH frequency peaked in the evening during the dry season. In addition, low and middle clouds were prevalent in Motuo for the period of observation in 2019. Understanding the characteristics of clouds over the TP will provide key validations of satellite measurements and promote research on cloud forces over the TP. • CVS at the front of the water vapor channel of the Yarlung Zangbo Grand Canyon (YZGC) was first measured. • The KaCR- CTHs were generally consistency with the FY-4A-CTHs. Negative deviations between them increased with rainfall rate. • Cloud cover frequently occurred over Motuo; clouds tended to form frequently at night and dissipate gradually in the daytime. • Two peaks in the CBHs distribution in Motuo were located at 0–1 km and 2–3 km. The CTHs peaked at 6–7 km. Low and middle clouds were prevalent. [ABSTRACT FROM AUTHOR]

Mêdog is located at the entrance of the water vapor channel of the Yarlung Tsangpo Great Canyon on the southeastern Tibetan Plateau (TP). In this study, the seasonal variation in the microphysical vertical structure of stratiform precipitation at the Mêdog site in 2022 was investigated using micro rain radar (MRR) observations, as there is a lack of similar studies in this region. The average melting layer height is the lowest in February, after which it gradually increases, reaches its peak in August, and then gradually decreases. For lower rain categories, the vertical distribution of small drops remains uniform in winter below the melting layer. The medium-sized drops show slight increases, leading to negative gradients in the microphysical profiles. Slight or evident decreases in concentrations of small drops are observed with decreasing height in the premonsoon, monsoon, and postmonsoon seasons, likely due to significant evaporation. The radar reflectivity, rain rate, and liquid water content profiles decrease with decreasing height according to the decrease in concentrations of small drops. With increasing rain rate, the drop size distribution (DSD) displays significant variations in winter, and the fall velocity decreases rapidly with decreasing height. In the premonsoon, monsoon, and postmonsoon seasons, the concentrations of large drops significantly decrease below the melting layer because of the breakup mechanism, leading to the decreases in the fall velocity profiles with decreasing height during these seasons. Raindrops with sizes ranging from 0.3–0.5 mm are predominant in terms of the total drop number concentration in all seasons. Precipitation in winter and postmonsoon seasons is mainly characterized by small raindrops, while that in premonsoon and monsoon seasons mainly comprises medium-sized raindrops. Understanding the seasonal variation in the vertical structure of precipitation in Mêdog will improve the radar quantitative estimation and the use of microphysical parameterization schemes in numerical weather forecast models over the TP. [ABSTRACT FROM AUTHOR]

The Qinghai-Tibetan plateau (QTP), also known as the Third Pole and the World Water Tower, is the largest and highest plateau with distinct and competing surface and subsurface processes. It is covered by a large layer of discontinuous and sporadic alpine permafrost which has degraded 10% during the past few decades. The average active layer thickness (ALT) increase rate is approximately 7.5 cm·yr-1 from 1995 to 2007, based on soil temperature measurements from 10 borehole sites along Qinghai-Tibetan Highway, and approximately 6.3 cm·yr-1, 2006-2010, using soil temperature profiles for 27 monitoring sites along Qinghai-Tibetan railway. In this study, we estimated the ALT and its AL thickening rate in the northern QTP near the railway using ALOS PALSAR L-band small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) data observed land subsidence and the corresponding ALT modeling. The InSAR estimated ALT and AL thickening rate were validated with ground-based observations from the borehole site WD4 within our study region, indicating excellent agreement. We concluded that we have generated high spatial resolution (30 m) and spatially-varying ALT and AL thickening rates, 2007-2009, over approximately an area of 150 km² of permafrost-covered region in the northern QTP. [ABSTRACT FROM AUTHOR]

Satellite altimetry has been widely used for inland water monitoring and modeling in the present decade. In this paper, the availability, data quality, and quantity of a number of spaceborne radar altimetry missions (including Topex/Poseidon (TP), ERS-2, Envisat, Jason-1/−2/−3, CryoSat-2, Saral, and Sentinel-3) are investigated. This is, to the best of our knowledge, the first paper to investigate the influences of onboard trackers, satellite flying directions, and land contamination on Level-1 waveforms and Level-2 measurements over large mountainous lakes. The analyses were conducted over eight Tibetan lakes, which are of varying sizes from ca. 93 to 1046 km2 and are sampled by multiple altimeters. From the results presented in this paper, it is demonstrated that the previous generation of altimeters, such as TP, Jason-1, ERS-2, and Envisat, shows a higher percentage of data unavailability and lower valid observation rates. Investigations of Level-1 waveforms show onboard tracker failing in locking on the lake surface, resulting in data loss or invalid measurements. In addition, the onboard tracking systems are sometimes unstable, resulting in larger along-track standard deviations (SD) (SD > 15 cm). In contrast, the recent generation of altimeters, i.e., Jason-3 and Sentinel-3 with open-loop tracking mode, significantly increases the data availability (> 90% passes and > 60% individual observations) and delivers higher precision measurements (SD around 10 cm). Moreover, the waveform leading edge is very consistent, indicating more stable onboard tracking. Higher quality Jason-3 and Sentinel-3 data allow monitoring of sub- and quasi-monthly lake variations, which are not revealed by e.g., TP and ERS-2 data due to poorer signal-to-noise ratios. Exceptionally, Saral Ka-band altimeter, operated in closed-loop tracking mode, is less affected by flying directions and land contamination (topography and landscapes), delivering high quality measurements (SD around 7 cm for 40 Hz). This study provides a comprehensive comparison of multiple altimeters in monitoring lakes in mountainous areas, and demonstrates the substantial improvements achieved in the past decades. However, care has to be taken when merging data from old generation altimetry missions over mountainous lakes. The lessons learned from these Tibetan lakes can be taken across to other mountain lakes. • Comprehensive assessment of multiple altimeters performance over Tibetan lakes. • Investigation of influences of onboard trackers on Level-1 waveforms and Level-2 measurements. • Onboard tracking failure is largely responsible for erroneous measurements contained in the GDR. • Distinctive improvements (∼ 100% data availability & < 10 cm precision) achieved during 1992–2021. [ABSTRACT FROM AUTHOR]

Whether tall storms produce heavy precipitation is currently a controversial topic. Here, we used seven years of observations from the dual-frequency precipitation radar and found that there is a rare but unique vertical precipitation structure over the Tibetan Plateau. The radar echo peaks above the freezing height, which we refer to as a "ghost echo". The existence of a ghost echo increases the echo-top height but suppresses the increase in droplet size below it, and therefore weakens the near-surface precipitation. Compared with normal echoes, ghost echoes appear more often in the afternoon. The potentially unstable environment produced by thermal forcing is the main cause of ghost echoes, rather than the dynamic factor of wind shear. The ghost echo, which is essentially a mechanism of ice-phase precipitation enhancement, represents a type of tall but weak precipitation. Its existence adds to our current perception of the nature of precipitation. [ABSTRACT FROM AUTHOR]

Interferometric synthetic aperture radar and teleseismic P‐wave data were combined to investigate the source rupture characteristics of the 2020 Mw 6.3 Yutian, China, earthquake. We first utilized the near‐field displacements together with 29 broadband teleseismic P waveforms to investigate the uniform slip model by using a Bayesian bootstrap optimization nonlinear inversion method to resolve the nucleation point location, origin time and fault geometrical parameters. Based on these results, the kinematic rupture process of the earthquake was inverted. We conclude that the 2020 Yutian earthquake occurred on a west‐dipping blind normal fault with a dip of ∼60° at the junction of Bayan Har block (BHB) and western Kunlun block (WKB). The rupture nucleation point was located at longitude = 82.435°E, latitude = 35.619°N, and a depth of 6.377 km, making it shallower than estimated from other point source inversions. The earthquake started at 21:05:20 UTC on June 25, 2020 and was delayed by ∼2.07 s compared with GeoForschungsZentrum. The rupture lasted for ∼12 s, with a total seismic moment of ∼3.28 × 1018 Nm, corresponding to a moment magnitude of 6.3. The slip was mainly confined between ∼3.0 and 9.0 km in depth and the peak slip was ∼1.40 m, which occurred at a depth of ∼6.377 km. The slip was predominantly normal slip with slight right‐lateral strike‐slip components, which agrees with the southeastward movement of the BHB relative to the WKB. Plain Language Summary: The June 25, 2020 Mw 6.3 Yutian earthquake occurred on a normal fault within the northwestern Tibetan Plateau, a region characterized by EW extension. Because the rough focal mechanism solutions and source locations based on seismic wave data reported by several institutes are different, they cannot be used to create a reliable fault model for inverting the kinematic rupture process of this moderate earthquake. The initial rupture point and origin time, which are the prior information needed for revealing the slip characteristics, are also unclear. To resolve these rupture parameters, both Sentinel‐1 interferometric synthetic aperture radar and teleseismic P‐wave data were collected. We found that the rupture mainly occurred in the shallow part of a ∼60° west‐dipping normal fault, the nucleation point was near the point of maximum slip, and the slip lasted ∼12 s and extended northward and southward. Our research has important significance for understanding earthquake disasters and deformation mechanisms of faults within the northwestern Tibetan Plateau. Key Points: Both interferometric synthetic aperture radar and teleseismic P wave are used to resolving the ambiguity of fault geometryThe rupture nucleation point and origin time were clarified by a Bayesian bootstrap optimization inversion methodRupture process of this earthquake is predominantly normal‐sip with slight right‐lateral strike‐slip components [ABSTRACT FROM AUTHOR]

Atmospheric heterogeneity mainly exposes itself as tropospheric-phase delay in Satellite Interferometric Synthetic Aperture radar (InSAR) observations, which smears or even overshadows the deformation component of InSAR measurements. In this study, we estimated the performance of four Global Atmospheric Models (GAMs), i.e. European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5), ERA-Interim (ERA-I), Modern-Era Retrospective analysis for Research and Applications v2 (MERRA2) and Generic Atmospheric Correction Online Service for InSAR (GACOS), for tropospheric-phase delay reduction in InSAR applications in the Tibetan plateau, of which ERA5 is the latest GAM released by ECMWF. We demonstrated the effectiveness of Atmospheric Phase Screen (APS) correction using the four GAMs for more than 700 Sentinel-1 Terrain Observation by Progressive Scans interferograms covering two study areas in the southern (R1) and northwest margins (R2) of the Tibetan plateau. Topography-correlated signals have been widely observed in these interferograms, which are most likely due to the APS effects. We calculated the Standard Deviations (SD) and Pearson's Correlation Coefficients (r) between InSAR Line of Sight measurements and topography before and after applying APS correction. The results show that the SDs of non-deformation areas from the GAMs decrease to approximately 4 mm from around 10 mm and 12 mm originally on average for R1 and R2, respectively, and the r after the APS correction are reduced below 0.4 from around 0.8 for the selected interferometric pairs. In addition, as the newly released GAM, ERA5 has similar performance with GACOS products and outperforms other models generally. This suggests that GAMs, particularly ERA5, have great potential in the APS correction for InSAR applications in the Tibetan plateau. [ABSTRACT FROM AUTHOR]

Wind profile light detection and ranging (LiDAR) is an important tool for observing features within the atmospheric boundary layer. Observations of the wind field and boundary layer height from coherent Doppler wind LiDARs (CDWLs) under sandy and dusty weather conditions were evaluated using observations from two CDWLs and one GTS radio sounding located at the northern edge of the Tibetan plateau from 1 May to 30 August 2021. The results showed that CDWL has good applicability in reproducing wind fields in dust, precipitation, and in clear-sky conditions, and that it is superior to the v wind field for real measurements of the u wind fields. In terms of the planetary boundary layer height (PBLH), the validity of the inversion of PBLH in dusty weather was higher than that under clear-sky conditions. It was found that the PBLH retrieved by the CDWL at 20:00 (BJT) was better than that at 08:00 (BJT). The diurnal variation amplitude of the PBLH before the occurrence of a sandstorm was larger than the diurnal variation amplitude of the PBLH occurring during a sandstorm. [ABSTRACT FROM AUTHOR]

This study presents a statistical analysis of the variability of the vertical structure of precipitation in the eastern downstream region of the Tibetan Plateau as measured by the Precipitation Radar (PR) on the National Aeronautics and Space Administration Tropical Rainfall Measuring Mission (TRMM) satellite. Data were analyzed over an 11-yr time span (January 2004-December 2014). The results show the seasonal and spatial variability of the storm height, freezing level, and bright band for different types of precipitation as well as the characteristics of intensity-related and type-related vertical profiles of reflectivity (VPR). Major findings were as follows: About 90% of the brightband peak reflectivity of stratiform precipitation was less than 32 dB Z, and 40% of the maximum reflectivity of convective precipitation exceeded 35 dB Z. The intensity of surface rainfall rates also depended on the shapes of VPRs. For stratiform precipitation, ice-snow aggregation was faster during moderate and heavy rainfall than it was in light rainfall. Since both the moisture and temperature are lower in winter, the transformation efficiency of hydrometeors becomes slower. Typical Ku-band representative climatological VPRs (CPRs) for stratiform precipitation have been created on the basis of the integration of normalized VPR shape for the given area and the rainfall intensity. All of the findings indicate that the developed CPRs can be used to improve surface precipitation estimates in regions with complex terrain where the ground-based radar net has limited visibility at low levels. [ABSTRACT FROM AUTHOR]