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Glacial Lake Outburst Flood (GLOF) events, particularly prevalent in Asia's High Mountain regions, pose a significant threat to downstream regions. However, limited understanding of triggering mechanisms and inadequate observations pose significant barriers for early warnings of impending GLOFs. The 2018 Nyalam GLOF event in southern Tibet offers a valuable opportunity for retrospective analysis. By combining optical and radar remote sensing images, meteorological data, and seismicity catalogs, we examined the spatiotemporal evolution, triggering factors, and the outburst mechanism of this event. Our analysis reveals a progressive retreat of 400–800 m for the parent glaciers between 1991 and 2018, increasing the runoff areas at glacier termini by 167% from 2015 to 2018 and contributing abundant meltwater to the glacial lake. In contrast, the lake size shrunk, potentially due to a weakening moraine dam confirmed by SAR interferometry, which detected continuous subsidence with a maximum line-of-sight (LOS) rate of ~120 mm/a over the preceding ~2.5 years. Additionally, temperature and precipitation in 2018 exceeded the prior decade's average. Notably, no major earthquakes preceded the event. Based on these observations, we propose a likely joint mechanism involving high temperatures, heavy precipitation, and dam instability. An elevated temperature and precipitation accelerated glacial melt, increasing lake water volume and seepage through the moraine dam. This ultimately compromised dam stability and led to its failure between 3 August 2018 and 6 August 2018. Our findings demonstrate the existence of precursory signs for impending GLOFs. By monitoring the spatiotemporal evolution of environmental factors and deformation, it is possible to evaluate glacial lake risk levels. This work contributes to a more comprehensive understanding of GLOF mechanisms and is of significant importance for future glacial lake risk assessments. [ABSTRACT FROM AUTHOR]

On 4 October 2023, a glacier lake outburst flood (GLOF) occurred at South Lhonak Lake in the northwest of Sikkim, India, posing a severe threat to downstream lives and property. Given the serious consequences of GLOFs, understanding their triggering factors is urgent. This paper conducts a comprehensive analysis of optical imagery and InSAR deformation results to study changes in the surrounding surface of the glacial lake before and after the GLOF event. To expedite the processing of massive InSAR data, an InSAR processing system based on the SBAS-InSAR data processing flow and the AI Earth cloud platform was developed. Sentinel-1 SAR images spanning from January 2021 to March 2024 were used to calculate surface deformation velocity. The evolution of the lake area and surface variations in the landslide area were observed using optical images. The results reveal a significant deformation area within the moraine encircling the lake before the GLOF, aligning with the area where the landslide ultimately occurred. Further research suggests a certain correlation between InSAR deformation results and multiple factors, such as rainfall, lake area, and slope. We speculate that heavy rainfall triggering landslides in the moraine may have contributed to breaching the moraine dam and causing the GLOF. Although the landslide region is relatively stable overall, the presence of a crack in the toparea of landslide raises concerns about potential secondary landslides. Our study may improve GLOF risk assessment and management, thereby mitigating or preventing their hazards. [ABSTRACT FROM AUTHOR]

Relevant studies have shown that methane gas has a close relationship with seismic activity. The concentration of methane released within a tectonic zone can reflect the intensity status of tectonic activities, which is important for seismic monitoring. In this study, the January 2020 Xinjiang Jiashi earthquake was taken as the research object, and the mature Robust Satellite Technique (RST) algorithm was used to characterize the L3-level methane product data from the hyperspectral sensor, Atmospheric Infrared Sounder (AIRS), installed on the Earth Observing System (EOS) AQUA satellite at the monthly scale, 8-day scale and daily scale. An analysis of the spatial and temporal distribution of methane was carried out for before and after the earthquake based on the 3D structural condition of the gas, and the 3D structural conditions of the 8-day scale were introduced. An 8-day scale 3D structural condition was introduced and migration validation was performed, and the results showed that (1) the seismic methane anomaly-extraction process proposed in this study is feasible; (2) the 3D contour features indicated that the methane anomalies that occurred before the Jiashi earthquake were caused by geogenic emissions; (3) the anomaly-extraction algorithm from this study did not extract the corresponding anomalies in the non-seismic year, which indicated that the anomaly-extraction algorithm of this study has some degree of feasibility; and (4) the migrated validation of the Wenchuan earthquake of May 2008 further suggested that methane anomalies at the time of the Wenchuan earthquake were caused by the earthquake. [ABSTRACT FROM AUTHOR]

Colorectal cancer (CRC) is a common malignant tumor that primarily affects the elderly population. Surgery is one of the main treatment modalities for CRC. Frailty is a prevalent characteristic among the elderly and a leading cause of mortality. The frailty index (FI) is a comprehensive tool for assessing patients' frailty status, quantifying indicators such as weight loss, fatigue, and nutritional status, to reflect the degree of frailty. In recent years, the FI has undergone modifications to more accurately evaluate the risk of surgical complications and prognosis in CRC patients. This review summarizes the methods for frailty assessment, the development and modifications of the FI, and compiles the research findings and applications of the FI in predicting surgical complications, postoperative recovery, and survival rates in CRC patients. Furthermore, limitations in the current modified frailty index (mFI) and future research directions are discussed. This review provides essential references for further understanding the role of frailty in CRC patients and the clinical application of the mFI. [ABSTRACT FROM AUTHOR]

Objective. This study aims to evaluate the impact and predictive value of the preoperative NPRI on short-term complications and long-term prognosis in patients undergoing laparoscopic radical surgery for colorectal cCancer (CRC). Methods. A total of 302 eligible CRC patients were included, assessing five inflammation—and nutrition-related markers and various clinical features for their predictive impact on postoperative outcomes. Emphasis was on the novel indicator NPRI to elucidate its prognostic and predictive value for perioperative risks. Results. Multivariate logistic regression analysis identified a history of abdominal surgery, prolonged surgical duration, CEA levels ≥5 ng/mL, and NPRI ≥ 3.94 × 10−2 as independent risk factors for postoperative complications in CRC patients. The Clavien–-Dindo complication grading system highlighted the close association between preoperative NPRI and both common and severe complications. Multivariate analysis also identified a history of abdominal surgery, tumor diameter ≥5 cm, poorly differentiated or undifferentiated tumors, and NPRI ≥ 2.87 × 10−2 as independent risk factors for shortened overall survival (OS). Additionally, a history of abdominal surgery, tumor maximum diameter ≥5 cm, tumor differentiation as poor/undifferentiated, NPRI ≥ 2.87 × 10−2, and TNM Stage III were determined as independent risk factors for shortened disease-free survival (DFS). Survival curve results showed significantly higher 5-year OS and DFS in the low NPRI group compared to the high NPRI group. The incorporation of NPRI into nomograms for OS and DFS, validated through calibration and decision curve analyses, attested to the excellent accuracy and practicality of these models. Conclusion. Preoperative NPRI independently predicts short-term complications and long-term prognosis in patients undergoing laparoscopic colorectal cancer surgery, enhancing predictive accuracy when incorporated into nomograms for patient survival. [ABSTRACT FROM AUTHOR]

Purpose: The albumin to alkaline phosphatase ratio (AAPR) is a newly developed blood biomarker that has been reported to have prognostic value in several types of cancers. The aim of this study was to investigate the predictive value of AAPR in overall survival after radical colon cancer surgery in patients with stage I-III colorectal cancer (CRC). Methods: The clinical data of 221 eligible patients with stage I ∼ III CRC were retrospectively analyzed. A series of survival analyses were performed to assess the prognostic value of AAPR. Univariate and multifactorial Cox analyses were performed to identify independent risk factors. Columnar graph prediction models were further constructed based on independent risk factors such as AAPR, and their predictive properties were validated. Results: The optimal cutoff value of preoperative AAPR for postoperative overall survival (OS) in patients undergoing laparoscopic radical CRC was.495 as shown by univariate and multifactorial Cox regression analysis. The factors of age ≤65 years, Tumor-Node-Metastasis (TNM) stage I-II, tumor grading (high/medium differentiation), CEA ≤5, and AAPR ≥.495 were associated with better OS (P <.05). Conclusions: Preoperative AAPR level was a good predictor of postoperative survival in patients undergoing laparoscopic radical CRC surgery, and AAPR <.495 was an independent risk factor for decreased postoperative OS. [ABSTRACT FROM AUTHOR]

A Mw 6.6 earthquake struck Menyuan, Qinghai, China, on 7 January 2022. To determine the rupture parameters of this event, the coseismic InSAR deformation fields were mapped and further employed to estimate the focal mechanism. The best-fitting solution emphasized that the 2022 Menyuan earthquake ruptured at the junction of the Tuolaishan fault and the Lenglongling fault. Both rupturing faults were dominated by sinistral strike-slip, and the main slip was concentrated on the shallow part of the rupture plane. The latter was the main rupture segment with a strike of 106° and a dip of 86°. The slip mainly occurred at depths of 0–8 km, and the rupture was exposed at the surface. The maximum slip reached ~3.5 m, which occurred mainly at a depth of 4 km. Joint analysis of the optimal slip model, relocated aftershocks, Coulomb stress change, and field observation suggested that the strain energy in the Tuolaishan fault may not have been fully released and needs further attention. Moreover, the 2022 Mw6.6 Menyuan earthquake caused a significant stress loading effect on the western Tuolaishan fault and eastern Lenglongling fault, which implies that the 2022 event increased the seismic hazard in these regions. [ABSTRACT FROM AUTHOR]

Although the atmospheric compensation models developed to date have been generally robust and effective for InSAR, how to choose the right atmospheric correction method for ground-based InSAR is worth studying. This paper uses different methods for atmospheric phase screen (APS) compensation based on studies of ground-based radar (GBR) to zero-baseline acquisitions over the Woda landslide in Sichuan, China. This landslide has a steep topography, thick fog, turbulent rivers and strong rains. Data were acquired at the Ku-band using a GAMMA Portable Radar Interferometer II (GPRI-II) in multiple campaigns (4 July 2019–13 July 2019). In 2019, the Miyun open-pit mine was also studied; the maximum deformation reached 4.03 mm/hour. The collected data were processed within one unit based on the small baseline set (SBAS) approach. The experimental results show the following (1) For long-distance monitoring with complex atmospheric disturbances, range- and/or height-dependent models fail. (2) The iterative decomposition (ITD) method can effectively address complex atmospheric disturbances. (3) If the threshold of wavelength is set to be large, the ITD method becomes a stratified model. [ABSTRACT FROM AUTHOR]

Detecting the slow motions of high and distant landslides in remote mountain areas has always been a problem. This paper takes the Woda landslide along the Jinsha River as an example to monitor landslide movement. Although some parts of the landslide body have been found to have moved in recent years, the timing and magnitude of motion have not been systematically monitored or interpreted. Here, we apply the SBAS time series strategy using 65-scene Sentinel-1A/B satellite InSAR images and study the spatial distribution and temporal behaviour of landslide movements between July 4, 2018, and August 29, 2020. Our research results show that the cumulative deformation on the left side of the landslide body with concentrated deformation was approximately 200 mm during the 2-year observation period. By calculating the relationship between the InSAR time series and the precipitation around the landslide, it is found that the landslide deformation is closely related to rainfall. GNSS technology is also deployed on the landslide mass and effectively complements InSAR technology. Simultaneously, based on the results of field surveys and hydrological data analysing the landslide's spatial deformation characteristics and deformation factors, the landslide deformation can also be inferred to be related to precipitation. The method used in this paper can be used for early recognition and early warning of high and remote landslides. [ABSTRACT FROM AUTHOR]

The Lenglongling Fault Zone (LLLFZ) is an important left‐lateral strike‐slip tectonic belt in the northeastern Tibetan Plateau (NETP), and the tectonic deformation and seismic activity of the LLLFZ reflect tectonic adjustments of the Qilian‐Haiyuan tectonic zone to the NETP. Although historical records of large earthquakes along the LLLFZ are not available, offset landforms reveal that large earthquakes have occurred. Therefore, offset landforms are used to study the seismic slip distribution to determine a fault slip model and earthquake recurrence behaviour based on an analysis of high‐resolution remote sensing images. Geomorphic markers associated with 316 systematically sinistrally deflected landforms were measured and analysed. The cumulative offset probability densities were analysed according to slip distributions measured along two segments of the fault. Offset density peaks in the eastern section of the fault decay exponentially with increasing offset size, suggesting that approximately seven palaeoearthquakes with an average slip of approximately 8 m occurred during the Holocene. The cumulative slips in the western segment increase gradually from west to east, with single‐event slips of approximately 2–3 m in the western part of the western segment and approximately 5–7 m in the eastern part. The seismic slip distributions of the LLLFZ indicate that the fault conforms to a quasi‐characteristic slip model. Both the eastern and western segments present typical left‐lateral strike‐slip movement. A magnitude of 8.0 was estimated for the LLLFZ palaeoearthquakes that occurred during the Holocene according to empirical relations. This study is helpful for understanding the tectonic deformation of the NETP. [ABSTRACT FROM AUTHOR]

For prediction of urban remote sensing surface temperature, cloud, cloud shadow and snow contamination lead to the failure of surface temperature inversion and vegetation‐related index calculation. A time series prediction framework of urban surface temperature under cloud interference is proposed in this paper. This is helpful to solve the problem of the impact of data loss on surface temperature prediction. Spatial and temporal variation trends of surface temperature and vegetation index are analyzed using Landsat 7/8 remote sensing data of 2010 to 2019 from Beijing. The geographically weighed regression (GWR) method is used to realize the simulation of surface temperature based on the current date. The deep learning prediction network based on convolution and long short‐term memory (LSTM) networks was constructed to predict the spatial distribution of surface temperature on the next observation date. The time series analysis shows that the NDBI is less than −0.2, which indicates that there may be cloud contamination. The land surface temperature (LST) modeling results show that the precision of estimation using GWR method on impervious surface and water bodies is superior compared to the vegetation area. For LST prediction using deep learning methods, the result of the prediction on surface temperature space distribution was relatively good. The purpose of this study is to make up for the missing data affected by cloud, snow, and other interference factors, and to be applied to the prediction of the spatial and temporal distributions of LST. This article is categorized under:Technologies > Machine Learning [ABSTRACT FROM AUTHOR]

In this study, multitemporal satellite images, unmanned aerial vehicle (UAV) photogrammetry and ground-based radar were utilized to investigate the formation mechanism and disaster features of different phases of the Xuyong landslide disaster that occurred in Sichuan Province on December 9, 2018. Field survey indicates that the estimated landslide volume is approximately 35000 m3. The landslide is a typical dualistic soil-rock structural landslide with bedding planes. The sliding surface is located in a thin layer of limestone which is characterized by the X-shaped conjugate joint planes. The steep slope has been cut and transformed by human disturbances, which have influenced the slope stability and the drainage of precipitation along the slope. Many factors, including the regional geological structure, stratum lithology, slope topography, landform morphology, and precipitation, have contributed to the Xuyong landslide during the pre-disaster phase. Post-disaster emergency observation revealed that subsequent deformation was located mainly along the back edge of the landslide, where the maximum surficial deformation reached only 18 mm/day over a small area, reflecting the low probability of a secondary landslide hazard. Our research provides significant guidelines for investigating potential landslide dangers in similar environments and for post-disaster emergency response using multiple remote sensing (RS) platforms. [ABSTRACT FROM AUTHOR]

Areas with sharp spatial changes in crustal structure are usually considered prone to strong earthquakes, especially late Cenozoic structural zones. However, quantitative relationships have not been established between the occurrence of earthquakes and the extent to which the crustal structure changes. The crustal structure can be reflected by gravity anomalies. In this study, we investigate the crustal structure variation in the eastern Tibetan Plateau based on the gravity data acquired by the Gravity field and steady‐state Ocean Circulation Explorer satellite. The multiscales wavelet decomposition and power spectrum methods are used to analyze the spatial variation of crustal structure at different depths. Based on a fourth‐order wavelet map, four variable factors are constructed to represent the spatial variations of the crustal structure, and their statistical relationship with earthquakes is studied. The results show that the changing rate of the gravity anomalies is significantly positively correlated with the occurrence of earthquakes. Areas of high earthquake hazards are places where the gravity field changes dramatically, usually with a value of 11°–18° for the SLP (slope) index. The assessment efficiency of the SLP increases with the earthquake magnitude. According to the SLP index, several regions are assessed to have a high level of risk for strong earthquakes in the eastern Tibetan Plateau, including the Longmenshan Fault belt, where a Ms8.0 earthquake occurred in 2008, thus demonstrating the promising implications of our method in the earthquake susceptibility assessment. Plain Language Summary: The distribution of earthquake epicenters is uneven in space. At present, it is generally believed that locations with crustal material changes are prone to earthquakes. However, not all earthquakes are distributed in these locations. To answer the questions of how many earthquakes are distributed in these locations and whether these characteristics can be used to predict the locations of earthquakes, we construct some factors based on gravity data and active faults and conduct statistical analyses in this paper. The results show that the greater is the variation in the gravity field, the higher is the frequency of earthquakes. The assessment efficiency of these characteristics increases with the earthquake magnitude. Key Points: Based on the fourth‐order wavelet detail map of gravity, we constructed four quantitative indexes to express the spatial changes in the crustEarthquakes are concentrated in the high‐value region of the slope (SLP) factor, approximately 11°‐18°The earthquake risk assessment efficiency of the SLP increases with the earthquake magnitude [ABSTRACT FROM AUTHOR]

This study investigates the 3 July 2015 (Mw=6.4) earthquake that affected Pishan County in Xinjiang, China. Using Synthetic Aperture Radar interferometry (InSAR), we mapped the near-field surface displacement of this event to better characterize the seismic source parameters. The inverted results suggest that a conjugate fault system could produce very similar deformation patterns as those observed in both ascending and descending InSAR observations, and the south-dipping fault is selected as the optimal fault responsible for the event. The selected fault was concentrated on a thrust fault with a strike of 112°, a dip of 25° and an average rake angle of 89°. The InSAR analysis reveals a fragmentation of the Western Kunlun north margin fault, and the overall deformation of the seismogenic fault is characterized by thrust motion, which is consistent with the transpressional tectonic characteristics of the major faults in this region. [ABSTRACT FROM AUTHOR]

The Yishu fault zone (YSFZ) is the most active fault in eastern China, and it is the location of an M 8.5 earthquake that occurred in 1668. However, topography and landforms in this area have been greatly altered by human activity during the previous three to four decades, which makes assessment of past earthquakes difficult. We therefore used a set of remote sensing images captured in the 1960s to evaluate the single-event and multievent cumulative offsets of streams along the fault. The local landforms have preserved the Holocene seismic offsets well despite the moderately humid climate in which the local landforms have evolved rapidly. Geomorphic markers associated with 401 systematically dextrally offset streams were analyzed and measured. These offset markers are considered to record seismic rupture processes. Cumulative offset probability densities were analyzed according to slip distributions along various subsections of the YSFZ. Four strong paleoearthquakes in addition to the 1668 earthquake were revealed by offset density peaks within the YSFZ, a finding that differs from those of previous studies. The average offset of the 1668 event is approximately 9 m. The cumulative offsets of the other four paleoseismic events are essentially multiples of the latest event. A single event ruptured more than 200 km of discontinuous fault traces. The similarity of the previous five earthquakes implies that rupturing of the YSFZ has followed a characteristic slip model during the Holocene, with a right-lateral slip rate of 2.2-2.6 mm/yr. We expect that the YSFZ is not due for another large earthquake for several thousand years. [ABSTRACT FROM AUTHOR]

The M 6.4 Menyuan earthquake occurred on the northern side of the Lenglongling fault (LLLF) in the mid-western of the Qilian-Haiyuan fault zone on January 21, 2016. The earthquake epicenter was distant from the Minle-Damaying and Huangcheng-Shuangta faults, eastern of the Northern Qilian Shan fault zone. A near northwest-striking rupture plane intersects the two faults at a certain angle. The focal mechanism solution shows that this was a thrust-type earthquake, slightly different from the strike-slip movement with a thrust component of the LLLF. Field geological mapping, tectonic geomorphology analysis, trench excavation and C dating reveal that (1) the LLLF has been obviously active since the Holocene, and may behave with characteristic slip behavior and produce M 7.3-7.5 earthquakes; (2) the LLLF appears as a flower structure in terms of structure style, and dips NNE at a steep angle; and (3) the most recent earthquake event occurred after 1815-1065 a BP. An associated fault, the Northern Lenglongling fault (NLLLF), is located at the northwestern end of the LLLF. Consequently, the NLLLF was continually subject to tectonic pushing effects from the left-lateral shear at the end of the LLLF, and, accordingly, it bent and rotated outward tectonically. Subsequently, the fault deviated from the dominant rupture azimuth and activity weakened. In the late Quaternary, it behaved as a thrust fault with no obvious deformation at the surface. This is indicated by the arc shape, with a micro-protrusion northeastward, and no geologic or geomorphic signs of surface rupturing since the late Quaternary. However, such faults could still rupture at depth, producing moderate-strong earthquakes. The geometric and kinematic properties of the NLLLF are in good agreement with the occurrence and kinematic properties of nodal plane 2, and with the distribution characteristics of the aftershocks and seismic intensity. Therefore, the NLLLF is a more suitable seismogenic structure for the M 6.4 Menyuan earthquake. In addition, the thrust movement of the NLLLF accommodates subsequent movement of the LLLF. During the historical evolution of the NLLLF, the LLLF and the NLLLF have affected the local topography through tectonic uplift. [ABSTRACT FROM AUTHOR]

This study utilized an unmanned aerial vehicle (UAV) photogrammetry system to acquire orthoimages and generate a digital elevation model (DEM) covering the southern part of the Anqiu–Juxian fault for geomorphological analysis and paleoearthquake identification. Six offset gullies were identified and analyzed on the orthoimages. Our results indicate that at least three large and several moderate earthquakes have occurred along the fault zone. Knickpoints recognized from the DEM reveal several paleoearthquakes. An average Holocene horizontal slip rate of 2.86 ± 0.35 mm yr −1 was estimated from the offset gullies, which is consistent with previous results from field surveys. The tectonic evolution of this fault zone is most likely related to subduction of the Pacific plate under the Eurasian plate, which gave rise to the left-lateral strike-slip and thrust movement of the Tan-Lu fault zone. This study provided valuable information regarding fault activity and paleoearthquake occurrence along the Anqiu–Juxian fault zone during the Holocene and demonstrated the potential of using UAVs for studies involving tectonic geomorphology. [ABSTRACT FROM AUTHOR]

The Damxung-Yangbajain rift is one of the most active north-south trending rifts in the south Tibetan Plateau, and it has been playing an important role in accommodating the east-west extension of the Tibetan Plateau. Both stream profiles on the Nyainqentanglha Range adjacent to the northwest part of the Damxung-Yangbajain rift and tectonic geomorphology in the north of the rift are analyzed to assess the spatial pattern and intensity of rock uplift which is related to neotectonic activity. A total of 85 stream profiles across the Nyainqentanglha Range are analyzed, and 111 knickpoints are interpreted. Most of these stream profiles are characterized by prominent convexities with two or more knickpoints, many of which are formed due to the strong rock uplift evidenced by abnormal concavity and extremely high steepness indices during the Quaternary. Neotectonic activity in this region is well replicated in the stream profile indices and offset landforms. Tectono-geomorphic analysis shows that the concavity and steepness indices correlate with the fault movements at many places. The Damxung-Yangbajain rift is characterized by left-lateral strike-slip in the north of Damxung and by normal movement in middle and southern parts. The middle and southern parts have been undergoing higher uplift than has the northern area. It is most likely that the strong uplift is related to the heat flow under the crust. Earthquakes occurring in the Damxung-Yangbajain rift, including a M8 in 1411 and M6.6 in 2008, are thought to be related to heat flow activity. All of the stream profile indices and tectonic geomorphology show that the Damxung-Yangbajain rift is not in a stable state. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Yangbajain contains the largest geothermal energy power station in China. Geothermal explorations in Yangbajain first started in 1976, and two plants were subsequently built in 1981 and 1986. A large amount of geothermal fluids have been extracted since then, leading to considerable surface subsidence around the geothermal fields. In this paper, InSAR time series analysis is applied to map the subsidence of the Yangbajain geothermal fields during the period from December 2011 to November 2012 using 16 senses of TerraSAR-X stripmap SAR images. In the case of the TerraSAR-X data, most orbital fringes were removed using precise orbits during the interferometric processing. However, residual orbital ramps remain in some interferograms due to the uncertainties in the TerraSAR-X orbits. To remove the residual orbital ramps, we estimated a best-fit ‘twisted plane’ for each epoch interferogram using quadratic polynomial models based on a network approach. This method removes most of the long-wavelength signals, including orbit ramps and atmospheric effects. The vertically stratified component (Topography Correlated Atmospheric Delay, TCAD) was also removed using a network approach. If the influence of seasonal frozen ground (SFG) is not taken into consideration, our results show that the subsidence rate around power plant I (the south plant) is approximately 20 mm/yr with a peak of 30 mm/yr. The subsidence rate around power plant II (the north plant) is approximately 10 mm/yr, when accounting for the influence of SFG on the power plant and its surrounding ground surface. Our results show that ground motion is caused by seasonal frozen ground and is strongly related to the temperature change. [ABSTRACT FROM PUBLISHER]

Using the Bam earthquake as an example, we apply the multiple-aperture interferometry (MAI) algorithm to measure the azimuth (AZI) displacement with multiple mode synthetic aperture radar (SAR) images (ScanSAR and image modes) and further on produce the 3-D coseismic displacement maps using well-known models: multiple independent interferometric SAR (InSAR) with different viewing angles and combining MAI with conventional InSAR. The 3-D displacement maps show that, besides accuracy of SAR observation, inversion model is another major perturbing factor limiting the accuracy of 3-D component reconstruction. That is, in the former model, the smaller the difference of incidence angles is, the more easily influenced by ill-conditioned systems the estimated parameters are. Based on characteristics of error sources of SAR observations, we classify observation errors into random error, systematic error, and gross error. Moreover, their characteristics of error propagation are analyzed in the two models, respectively. Error propagation analysis indicates that random errors only affect variability of inversion result, while systematic error and gross error cause not only variability but also bias or uncertainty in estimated parameters. The presented error analysis method provides a more comprehensive understanding of bias or uncertainty of 3-D estimated components, which will be a useful tool for evaluating errors in displacement fields obtained from SAR observations. In this letter, we also group multiple InSAR and MAI observations to estimate 3-D components using weighted least squares whose weights are given by the Förstner posterior variance estimation, which may avoid an ill-conditioned system, reducing line-of-sight and AZI random noises and improving accuracies of estimated 3-D components. [ABSTRACT FROM PUBLISHER]

Due to temporal and spatial decorrelation and other noise, the integer-cycle jumps always appear in the unwrapped phase. It is well known that phase unwrapping errors represent one of the major limitations of Interferometric SAR (InSAR). A phase closure method is presented to detect and correct phase unwrapping errors for discrete coherent points in InSAR time series analysis. Its application to ENVISAT Advanced Synthetic Aperture Radar (ASAR) data over the coastal zone of Cang-zhou, Hebei Province showed a significant improvement in the InSAR time series results, with the number of valid coherent pixels increasing from 68 000 to 186 400 and the root mean square (RMS) decreasing from 13. 1 mm to 5. 3 mm and 17. 5 mm to 4. 3 mm for two deforming areas respectively. [ABSTRACT FROM AUTHOR]

Highlights: [•] Detailed crustal structure and Moho topography of the North China are inverted. [•] Three typical gravity models transverse to major active blocks and active faults are constructed. [•] Density of the North China presents inhomogeneous feature in lateral direction. [•] Strong seismical activity and its tectonic mechanism of the North China are studied. [Copyright &y& Elsevier]

Abstract: In this paper, Bouguer gravity data were used to invert crustal structure of the Chuan-Dian region of China. Both multi-scale wavelet analysis and density interface inversive methods were adopted. Three gravity models transverse to major blocks were constructed. Our research indicates that great differences exist in crustal structures between the Eastern Basin and the Western plate, and crustal structures of Chuan-Dian region are closely correlated with tectonic activities of the Eastern Tibetan Plateau. The Western Sichuan platform experienced strong deformation due to eastward extrusion of the Tibetan Plateau. This led to heaving of the upper crust and thickening of the lower crust. The low-density crusts of Western Blocks were deformed by many high-angle faults, and most of these faults cut through to the middle crust. Density structures of upper and middle crusts are restricted by the regional tectonic stress fields and fault zones. The lower crust was deformed by folding, inducing high- and low-density anomalies alternatively. Rocks beneath the Longmenshan sub-block and the Northwestern sub-block of Sichuan were severely broken. For strong eastward extrusion of the plateau, large areas of low-density anomaly were observed in the lower crust. Adjusted by gravity isostasy, the lower crusts of the Chuan-Dian block and the Songpan–Garze block have thickened intensely. Density structures present highly inhomogeneous manner in lateral direction throughout the Western Block. Crustal densities of the Sichuan Basin are much more homogeneous, and the whole lithosphere is denser than that of Western Block. In transitional area between the South China Block and the Chuan-Dian Block, with the decreasing of crustal density, crustal stability is also depressed. In addition, we obtained a detailed map of Moho using variable density model. The Moho topography undulates greatly beneath the Chuan-Dian region. The maximum crustal thickness difference of the Chuan-Dian region is about 30km. Moho depth across Longmenshan descends from 43km in the east to nearly 60km in the west. The maximum and minimum Moho depths of the Western Blocks are about 65 and 46km in the Litang area and in the Panzhihua area respectively. Structural directions of Moho topography are consistent with strikes of fault tectonics. [Copyright &y& Elsevier]

• Potential field inversion and 3-D visualization are revealled from Bouguer gravity data. • There is a low-density body in the lower crust of the Longmen Shan fault zone. • The density structure of the fault zone is complex and the Moho depth is an abrupt change. • A counter-clockwise rotation of the Sichuan Basin is shown by source edge detection. • The rotation is one of the important dynamic backgrounds for the 2008 Wenchuan earthquake. In this paper, we adopt the methods of Euler deconvolution, source parameter imaging (SPI), source edge detection (SED), inversion of the Moho interface, and three-dimensional (3-D) visualization of the crust for the inversion of the Bouguer gravity anomaly of the Longmen Shan and adjacent regions, analyse the 3-D structure, deep structure, and deformation characteristics of the crust, and investigate the cause of the deep seismogenic environment and the Wenchuan earthquake. The research indicates that the Longmen Shan fault zone is characterized by a NE-trending large gravity gradient zone with a gradient value that exceeds 3.7 mGal/km. The Euler diagram reveals that there is a low-density anomaly body in the lower crust of the Longmen Shan fault zone that is a NE-trending narrow strip approximately 100 km long, 65 km wide and 35–50 km deep. The Songpan-Garze block on the northwest side does not have the material source and pathway of the lower crustal flow in the Euler diagram. Therefore, the low-density anomaly body is related to the upwelling of the mantle heat flow below it. In comparison with the Songpan-Garze and Chuan-Dian blocks, the strength of the field source of the Sichuan Basin is high (−175 to −96 mGal), indicating that the average density of the crust is high, and the depth of the field source is stable at 15–25 km. The SED map reveals that there has been counter-clockwise rotation of the Sichuan Basin since the Cenozoic. The SPI shows that the Longmen Shan fault zone is narrowly located in the beaded linear "shallow source anomaly" belt and that its two sides are stable areas of deep source anomalies, indicating characteristics of crustal hardness on both sides, so that it is prone to accumulate stress and strain. The Moho depth across the Longmen Shan descends from 41.8 km in the east to 61.6 km in the west. The complex intersection of high-density and low-density anomaly bodies appears in the deep part of the Longmen Shan tectonic belt, and the crustal structure is fragmented. Moreover, there is a strong abrupt change in the Moho topography, and therefore, this region has a deep environment for the genesis of strong earthquakes. The dextral strike-slip movement of the Longmen Shan fault zone is caused by the movement of the Songpan-Garze block and the counter-clockwise rotation of the Sichuan Basin; therefore, the counter-clockwise rotation of the Sichuan Basin is one of the important dynamic backgrounds for the 2008 Wenchuan earthquake. [ABSTRACT FROM AUTHOR]

The appearance of the surface rupture of the NW-striking Xiaoyudong Fault during the Wenchuan earthquake has attracted attentions of scholars and subsequently aroused debates about it. The size and tectonic significance of this fault is the key of the debates. Based on maps of gravity and magnetic in the scale of 1:500,000, the wavelet multi-scale method and the power spectrum method were used to obtain the wavelet fault analysis maps at different scales with average field source depths. Furthermore, the Euler deconvolution solutions of magnetic were determined and a simple model of the crust was built through the joint inversion of gravity and aeromagnetic data to analyze the penetration depth of the Xiaoyudong Fault. Combining these data with aftershock relocation data of Wenchuan earthquake provides better understanding of the Xiaoyudong Fault. We found that the Xiaoyudong Fault strikes NW cutting through the Pengguan and Xuelongbao complexes, and extending to the Yibasan area of Dazhou in Sichuan Province. The total length of the Xiaoyudong Fault is estimated to be 100 km, and its depth of penetration is less than 20 km, indicative of the Xiaoyudong Fault as a part of the decollement structural system. The parallel Miyaluo Fault is on the west of the Xiaoyudong Fault, cuts to a depth of less than 20 km, and is also a part of the same decollement structural system. The Xiaoyudong and Miyaluo faults are both part of the NW-striking tectonic system in the Songpan–Ganzi Fold Belt. The Xiaoyudong Fault was active during the Mesozoic and was reactivated during the earthquake with the Longmenshan Fault Belt under the present tectonic stress regime. However, only the southern most part of the Xiaoyudong Fault ruptured at the ground surface in the Wenchuan earthquake. [ABSTRACT FROM AUTHOR]