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[Display omitted] [ABSTRACT FROM AUTHOR]

Previous studies using paleoseismic trenches and numerical models proposed two different fault rupture models for the Pingdingshan-Annanba segments of the Altyn Tagh Fault, which are both poorly validated because of a lack of measurements of surface rupture displacements. In this paper, we use high-resolution satellite imagery to measure offset geomorphic markers. Taking the fault geometry into consideration, the most likely paleoseismic rupture parameters are determined by comparing the results of the cumulative offset probability densities (COPDs) and the empirical relationships of seismic parameter. The results show that the most recent earthquake (1270A.D.-1775A.D.) along the Suoerkuli segment only ruptured the Suoerkuli Valley, with a surface rupture length of 140 km, an average horizontal displacement of 3.12 m and a moment magnitude (Mw) of 7.4–7.6. The penultimate earthquake (676A.D.-1347A.D.) ruptured both the Annanba segment and part of the Suoerkuli segment with an average horizontal displacement of greater than 5 m, a surface rupture length of 120–260 km and Mw 7.4–7.8. The rupture parameters of the above two earthquakes demonstrate that the Suoerkuli and Annanba segments are individual fault segments which can rupture independently with a surface rupture length more than 100 km. The Pingdingshan double bend to the west of the Suoerkuli segment is likely to be an endpoint that inhibits the rupture propagation towards further west. [ABSTRACT FROM AUTHOR]

Based on the dense GPS velocity field in the northeastern margin of the Tibetan Plateau from 1999 to 2016, we have produced the deformation and strain characteristics of the Haiyuan fault and the Liupanshan fault. Estimated long-term slip rate along the Haiyuan-Liupanshan fault zones show a gradual decrease from 6.4 ± 1.6 mm/yr at the Tuolaishan fault to 2.9 ± 1.2 mm/yr at the Southern Liupanshan fault. Left-lateral thrusting movement was inverted for the Xiangshan-Tianjingshan fault (XS-TJS), which has an average slip rate of 2.1 ± 3.4 mm/yr during the study period. We also calculated the heterogeneous distribution of interseismic coupling along the fault zones. Our result also shows the locking depth of the Tianzhu seismic gap is ∼22 km. The slip rate deficit, the seismic moment accumulation rate, and the Coulomb stress accumulation rate are high on the fault planes, whereas the second invariant of the strain rate is low at the surface. The Liupanshan fault is locked to a depth of ∼23 km, and the corresponding seismic moment accumulation rate on the fault plane is high, while the strain rate at the surface is low. The accumulated strain along the Tianzhu seismic gap and the Liupanshan fault could be balanced by earthquakes with magnitudes of Mw7.9 and Mw7.4, considering the absence of large earthquakes over the last 1000 years and 1400 years respectively. The Haiyuan segments had ruptured during 1920 Haiyuan earthquake, and the estimated locking depth for period 1999–2016 is 5–10 km. Its seismic moment accumulation rate at depth is low and the strain rate at the surface is high. Our result indicates that 70% of the strike-slip along the Haiyuan segments transforms into thrusting along the Liupanshan fault, while the remaining 30% is related to the orogeny of the Liupanshan. For slip between the Haiyuan fault and the XS-TJS, about 27–34% of the slip is partitioned on the XS-TJS. [ABSTRACT FROM AUTHOR]

The July 3rd, 2015 Pishan, China Mw 6.4 earthquake occurred within the Hetian fold belt, a frontal thrust region between the Northwestern Tibetan Plateau and the Tarim basin. We investigate the fault geometry and the rupture process of the Pishan earthquake based on joint inversion of teleseismic body waves and InSAR measurements. Our results show that the top of the fault that ruptured in the Pishan earthquake is buried 5 ± 2 km beneath the surface and that the earthquake ruptured only a segment of a deeply-seated detachment lying under the Hetian fold belt. Our inferred coseismic slip model shows two slip asperities, located in the depth range of about 7–9 km and 10–11 km. Additionally, we resolve a slip deficit region between the slip asperities, which might indicate friction heterogeneity on the fault plane. The earthquake ruptured for ∼15 s, releasing a total seismic moment of 4.7 × 10 18 N m. We also show that the latest Pishan earthquake caused positive Coulomb stress changes on back thrust faults, potentially decreasing the time to the next earthquake on those faults. Based on our Pishan coseismic slip model, along with both the trend of the anticline system and the pattern of coseismic deformation, we envision an ongoing east-west extensional growth of the anticlines in the Western Kunlun frontal thrust region in addition to the northern underthrusting of the Northwestern Tibetan Plateau below the Tarim basin. [ABSTRACT FROM AUTHOR]

GPS-derived horizontal velocities, geologic fault slip rates and earthquake-derived fault slip vector azimuths are inverted simultaneously for fault coupling and slip rate deficit on the Haiyuan-Liupanshan fault in the northeastern margin of the Tibetan Plateau. Along the Haiyuan fault, the results show 3.2–6.2 mm/yr of left-lateral strike-slip, and the strike-slip transformed into thrusting deformation (2.8–3.5 mm/yr) along the Liupanshan fault. The results suggest full coupling down to ∼10 km along the Haiyuan fault. Significant portions from the Jinqianghe fault to the Maomaoshan fault, however, are locked to ∼23 km depth. The abrupt change in fault coupling coincides with the Tianzhu seismic gap. High slip rate deficit (3.0–4.5 mm/yr) and seismic moment accumulation rate are also interpreted along the seismic gap. The Liupanshan fault is locked to 15–20 km depth. A high seismic moment accumulation rate, low slip rate deficit (2.0–3.2 mm/yr) and scarcity of large seismic event over the last 1400 years may imply high strain accumulation on the fault. The results demonstrate that crustal deformation in the northeastern Tibetan Plateau is dominated by elastic block rotation. We also conclude that deformation due to fault coupling is limited along the near-field (less than 50 km with velocities less than 2 mm/yr) of the Haiyuan-Liupanshan fault. [ABSTRACT FROM AUTHOR]

Using SAR interferometry on C band Envisat descending track and L band ALOS ascending track SAR images, respectively, we firstly obtain two coseismic deformation fields and one postseismic deformation of the 2010 Yushu earthquake, Tibet, China. In the meanwhile, we also obtain the azimuthal coseismic deformation of the Yushu event by Multi Aperture Interferometry (MAI) technique. With the 3 components of one-dimensional coseismic InSAR measurements, we resolve the complete 3-dimensional deformation of the 2010 Yushu event, which shows conformity and complexity to left lateral slip mechanism. The horizontal deformation is basically consistent with a sinistral slip event; whereas the vertical displacement does show certain level of complexity, which we argue is indicative of local fault geometry variation. Based on the InSAR data and elastic dislocation assumption, we invert for coseismic fault slip and early after-slip of the Yushu event. Our inversion results show major coseismic left lateral strike slip with only minor thrust component. The after-slip model fills most of the slip gaps left by the coseismic fault slip and finds a complementary slip distribution to the coseismic fault slip, which is a good indicator that future earthquake potential on the Yushu segment has been significantly reduced. [ABSTRACT FROM AUTHOR]

Abstract: We applied a joint inversion of teleseismic data and InSAR measurements, aiming at obtaining a robust rupture process and slip distribution of the 2010 Yushu earthquake, through reducing the trade-off between slip timing and location. With the condition of the final static deformation of InSAR measurements, the rupture history can be achieved with more confidence. Surface offset constraint is also applied to our inversion. Through synthetic data inversion we find that InSAR data can resolve better fault slip at near surface depth range of 0–15km than teleseismic data; yet it has much poorer resolution at near hypocenter area, where teleseismic data has a relatively better resolution. Our final joint inversion results show that the 2010 Yushu earthquake has an essential rupture time around 20s, during which 90% of the seismic moment has been released. Two peak energy releasing moments occur at 8 and 12s after the earthquake initiation, respectively. The fault slip breaks the surface at most segments of the total 76km fault model and the maximum slip reaches 2.2m. We also find two peak-slip asperities, one at near hypocentral area, mainly distributed at depth around 10–15km; the other distributed in a large area at the eastern segments at near surface. Our most robust estimation of the seismic moment reaches 2.30×1019 N.m, equivalent to a moment magnitude of M w 6.9. [Copyright &y& Elsevier]

Abstract: On 21 March 2008, an Ms7.3 earthquake occurred at Yutian County, Xinjiang Uygur Autonomous Region, which is in the same year as 2008 Mw 7.9 Wenchuan earthquake. These two earthquakes both took place in the Bayar Har block, while Yutian earthquake is located in the west edge and Wenchuan earthquake is in the east. The research on source characteristics of Yutian earthquake can serve to better understand Wenchuan earthquake mechanism. We attempt to reveal the features of the causative fault of Yutian shock and its co-seismic deformation field by a sensitivity-based iterative fitting (SBIF) method. Our work is based on analysis and interpretation to high-resolution satellite (Quickbird) images as well as D-InSAR data from the satellite Envisat ASAR, in conjunction with the analysis of seismicity, focal mechanism solutions and active tectonics in this region. The result shows that the 22km long, nearly NS trending surface rupture zone by this event lies on a range-front alluvial platform in the Qira County. It is characterized by distinct linear traces and a simple structure with 1–3m-wide individual seams and maximum 6.5m width of a collapse fracture. Along the rupture zone are seen many secondary fractures and fault-bounded blocks by collapse, exhibiting remarkable extension. The co-seismic deformation affected a big range 100km×40km. D-InSAR analysis indicates that the interferometric deformation field is dominated by extensional faulting with a small strike-slip component. Along the causative fault, the western wall fell down and the eastern wall, that is the active unit, rose up, both with westerly vergence. The maximum subsidence displacement is ∼2.6m in the LOS, and the maximum uplift is 1.2m. The maximum relative vertical dislocation reaches 4.1m, which is 10km distant from the starting rupture point to south. The 42km-long seismogenic fault in the subsurface extends in NS direction as an arc, and it dipping angle changes from 70° near the surface to 52° at depth ∼10km. The slip on the fault plane is concentrated in the depth range 0–8km, forming a belt of length 30km along strike on the fault plane. There are three areas of concentrating slip, in which the largest slip is 10.5m located at the area 10km distant from the initial point of the rupture. [Copyright &y& Elsevier]

[Display omitted] • AIRS data revealed pre-seismic surface temperature anomalies. • The high commission rate reduces the practicality of earthquake prediction. • The accuracy and omission rates of forecasting in Eastern Japan reached their peaks. • It's reasonable to apply this framework for assessing earthquake forecasting ability. There are growing observational evidences that various geophysical anomalies precede large earthquakes. However, the reliability of these anomalies for earthquake forecasting is controversial, and therefore more consistent assessment of forecasting ability is required. A framework for investigating pre-seismic anomaly detection using essential statistical indicators before global earthquakes is proposed. Surface temperature (ST) data from the Atmospheric Infrared Sounder (AIRS) sensor were used to realize this framework. First, seismic-related ST anomalies were identified, and then the statistical characteristics of forecasting ability for three indicators (accuracy, missed detection, and false alarm) were calculated in retrospective and prospective ways. The ST anomalies displayed some aggregation effects. Negative anomalies mainly concentrated on epicenters and to the north, while positive anomalies were found on the periphery; neither were strongly dependent on earthquake magnitude. The temporal evolution of forecasting metrics was relatively stable for the period 2010–2018. Mean accuracy, missed detection, and false alarm ratios were 6.01%, 1.60%, and 92.39%, respectively. Accuracy and missed detection ratios showed some spatial correlation and both peaked in the same area (e.g., eastern Japan); however, most areas showed very high false alarm ratios. Based on our findings, the combination of AIRS ST data and the Z-score anomaly detection algorithm to predict short-term earthquakes is currently not practical; the possibility of earthquake forecasting based on satellite thermal infrared measurements remains a huge challenge. However, our results confirmed the efficiency of this framework for quantitatively evaluating earthquake forecasting ability. This approach could be applied to various geophysical parameters and anomaly detection methods. [ABSTRACT FROM AUTHOR]

Abstract The Mw6.9 Yushu earthquake occurred on 14 April 2010, in Qinghai, China; the largest aftershock, a Mw5.8 event, occurred west of the mainshock on 29 May 2010 (˜40 days later). The aftershock had a different focal mechanism from the mainshock. Furthermore, seismicity after 29 May showed different spatial characteristics in terms of focal depth and distribution direction. To better understand the faulting and the relationship between these two events, we derived the whole displacement field caused by the Yushu mainshock and the Mw5.8 aftershock based on multi-perspective Interferometric Synthetic Aperture Radar (InSAR) data. We then conducted a robust inversion of the slip distribution jointly constrained by InSAR and GPS data. The results indicate that the Mw5.8 aftershock produced a separated deformation field with significant displacement changes of up to ˜4–6 cm, which indicates another intersecting ruptured fault at the west end of the Yushu fault. The slip distribution shows a 75-km NW rupture with a maximum slip of ˜2.1 m at a depth of ˜0–10 km on the main Yushu fault, and a 20 km NE rupture with peak slip of ˜0.4 m at a depth of ˜5–15 km on a vertical hidden fault. Both events showed a dominant left-lateral component. The total rupture length associated with the 2010 Yushu earthquake sequence reached ˜95 km. By calculating Coulomb stress changes, we confirmed that the mainshock triggered the Mw5.8 aftershock. Our results imply that the increased stress at the western end of the Yushu fault caused by the mainshock rupture may have played an important role in transferring the rupture plane from the Yushu fault to the NE hidden fault. [ABSTRACT FROM AUTHOR]

We have generated a more than 500 km long postseismic deformation rate map and cumulative displacement time series in the central Bayankala Block of the Tibetan Plateau using ENVISAT/ASAR data from 2003 to 2010 by the π-RATE stacking algorithm. This rate map spans a period of ∼7.2 years and reveals that postseismic motion of 2001 Kokoxili earthquake exhibits a striking signal, dominating crustal deformation of the central Bayankala Block with a cross-fault magnitude ∼9–11 mm/yr in line of sight (LOS) (∼93.1°E). The southern and northern parts of the postseismic deformation field exhibit different patterns and variable magnitudes, reflecting asymmetry of the displacement distribution. Postseismic motion affects eastward extrusion of the central Bayankala Block, which reaches ∼15 km north of the Ganzi-Yushu fault. To further investigate viscoelastic relaxation of the lower crust in this area after approximately two years, E-M, E-M-M and E-S models are constructed. The result shows that the best fit viscosity for the lower crust is about 1 × 10 19  Pa·s. Comparison between cumulative displacements resolved by these three models shows that viscoelastic relaxation of the lower crust makes the most significant contribution to postseismic stress relaxation after 2001 event. [ABSTRACT FROM AUTHOR]

An earthquake of seismic moment magnitude (Mw)6.3 occurred in southern Taiwan on February 6th, 2016. In this paper, we use differential interferometric synthetic aperture radar (D-InSAR) technology and data from the Sentinel-1A(S-1A)/IW radar satellite to estimate the coseismic deformation of this event. On the basis of ascending data, InSAR analysis reveals a circle-like uplift area, 45 km in diameter, 20 km northwest of the epicenter, that has a maximum line of sight (LOS) displacement of 12 cm. South and east of this uplift area, minor subsidence occurred, while descending data indicated uplift in the west and sink in the east, with maximum values of 8.0 cm and 6.0 cm, respectively. Displacements are continuously distributed across the entire deformed region, implying that the seismogenic fault did not pierce the Earth’s surface. Based on these InSAR displacements coupled with GPS observations, we inverted the distribution of source slip using an elastic half-space fault model both separately and jointly. Four kinds of inversion results consistently show a slip concentration to the northwest of the epicenter, with maximum slip in the range 0.35–0.55 m confined to depths of 6–15 km in the crust. The source fault is dominated by thrust with left-lateral strike slip; joint inversion using InSAR ascending and descending data, as well as GPS data, resulted in maximum slip of 0.44 m, within the range determined by separate inversions. Inversion results show that this was a Mw6.25 earthquake, consistent with measurements collected by the United States Geological Survey (USGS). [ABSTRACT FROM AUTHOR]

Coseismic deformation fields caused by the moment magnitude (Mw)7.8 mainshock and Mw7.3 aftershock of the 2015 Gorkha-Nepal earthquake are obtained by analyzing Sentinel-1A/IW ascending and descending interferometry data. Results show that the deformation field associated with the Mw7.8 mainshock roughly resembles a prolate ellipse, extending from the epicenter about 20° east by south. The main region of deformation is about 160 km by 110 km, comprising a large southern area of uplift, and a small northern area of subsidence. Assuming that rupture occurred in a homogeneous elastic half-space, the coseismic fault slip models of the mainshock and aftershock are inverted based on a shallow dip fault constrained by the three data sets, Sentinel-1A/IW descending data, ascending data, and ALOS-2 descending data, separately or in combination. Mainshock slip distributions generated from all three data sets are similar, and inversion constrained by all three in combination reveal a comprehensive fault slip model. Indeed, coseismic slip is mainly distributed within a narrow 40 km zone to the north of the Main Frontal Trust (MFT), and at 6–15 km subsurface depth. In addition, the maximum slip in this event was about 5.1 m, the Mw7.8 mainshock ruptured the deep part of the seismogenic zone, while the region between the southern boundary of the rupture area and the MFT remained locked. Therefore, a considerable earthquake risk remains to the south of Kathmandu. The inverted coseismic slip of the Mw7.3 aftershock was concentrated in a small area, close to, and southeast of the epicenter, with maximum displacement of about 3 m. Finally, because there is no overlap between the two slip areas of the mainshock and aftershock, the gap between them, about 15 km in length, has additional potential to generate future earthquakes. [ABSTRACT FROM AUTHOR]

The spatial pattern and rate of strain accumulation on a fault during the pre- and inter-seismic phases are very important for interpreting the mechanism of earthquakes and evaluating seismic potentials. Here we use global positioning system (GPS) data and the block-dislocation model to invert for the locking degree and slip rate deficit of the Main Himalayan Thrust (MHT) fault in the southern margin of Tibet before the 2015 M w 7.9 Nepal earthquake. Results show that the locking depth and slip rate deficit increase from the west to the east. Along the western segment of the MHT fault (80°E–84°E), the locking depth is estimated to be 12–17 km with a slip rate deficit of 0–5 mm/a; along the central Nepal segment (84°E–87°E), the locking depth is 16–21 km with a slip rate deficit of 6–10 mm/a, whilst along the eastern segment (87°E–90°E), the locking depth increases to 23–26 km with a slip rate deficit of 8–13 mm/a. The 2015 Nepal earthquake initiated at the boundary between the western and central segments, an area with as where the slip rate deficit varies dramatically from 0 to 9 mm/a within 50 km resulting in high energy gradients. High strain concentration along the central and eastern segments leads to unilateral propagation of the rupture to the east. Given the paucity of large seismic events over the previous decades and the current high slip rate deficit, seismic hazard on the eastern Nepal segment remains high. [ABSTRACT FROM AUTHOR]

The 2013 Mw6.8 Lushan, China earthquake occurred in the southwestern end of the Longmenshan fault zone. We jointly invert local strong motion data and geodetic measurements of coseismic surface deformation, including GPS and InSAR, to obtain a robust model of the rupture process of the 2013 Lushan earthquake. Our joint inversion best model involves the rupture of two opposing faults during the Lushan earthquake, a main fault and a secondary fault. It is only when the secondary fault is included that both the GPS and InSAR measurements are fit along with the near-field strong motion. Over 75% of the computed moment was released in slip on the main fault segment, a northwest dipping, listric thrust fault, with buried thrust and dextral strike-slip at hypocenter depths, and with only minor slip closer to the surface. The secondary fault mainly involved oblique thrust slip or pure dextral strike-slip at shallower depths, and accounts for just under 24% of the moment released in the Lushan earthquake. Coulomb stress changes of about 0.5 MPa on the secondary fault segment at the time coseismic slip initiated on that fault indicate that slip was likely triggered by the coseismic slip on the main blind thrust fault. Our coseismic slip model is consistent with a sub-horizontal and east–west to southeast–northwest trending most compressive stress. Our inferred coseismic slip model is also consistent with previous GPS derived models of strain accumulation on the Longmenshan fault system. [ABSTRACT FROM AUTHOR]

Abstract: We obtained the coseismic deformation field of the Ms7.1 earthquake in Yushu, Qinghai, China on 14 April 2010 using L band and C band SAR images. The results show that the deformation fields derived from L and C bands separately are consistent in general. They are all characterized by concentric elliptic interference fringes surrounding a NW trending fault with two local intensively deformed regions. Meanwhile they have small differences in area coverage of the deformation field, magnitude of LOS displacements and other details of deformation nearby the fault. The deformation from C band and L band covers 89∗59km square and 77∗43km square, with maximum displacements of about 45cm and 65cm in the radar line of sight, respectively. Using these two kinds of InSAR measurements separately and jointly, we constructed a three-segment fault model and inverted the coseismic fault slip of the Yushu event. The inversion results show that the slip distributions constrained by the two kinds of inSAR data are in agreement on the whole. They all indicate two concentration regions of slip distribution, one is located near the Jiegu town on the southeastern segment of the Yushu fault with a large area and the maximum slip of 2.4m, and the other is at the epicenter on the northwestern segment of the fault with a relatively small area. There are also discrepancies between the two kinds of slip distribution models. In general, the scale, magnitude, and depth of slip distribution constrained by C band ASAR data are larger than that by L band PALSAR data. The slip distribution from a joint inversion of the two kinds of SAR data is considered to be the most robust model compared to the results of that constrained by L band SAR data or C band SAR data alone. [Copyright &y& Elsevier]

Abstract: We invert the fault slips of 2011 Mw 9.0 Tohoku earthquake with constraints from GPS, InSAR and seafloor GPS/acoustic measurements. The seismogenic fault geometry is constructed according to slab contours of Japan Trench. Steepest Descent method and Laplacian smoothing are used to solve slip distribution and regularize the solution. We firstly take GPS displacement in two postseismic periods, the first 8h right after mainshock from 5:55 to 14:00 UTC and the 13days from 12 March 2011 to 25 March 2011, to solve for the postseismic slips. The solved postseismic slips are adopted to remove postseismic signal in InSAR and seafloor observation. In order to estimate the effect of postseismic correction and contribution from different geodetic datasets, we invert several coseismic slips with constraints from GPS (Model 1), corrected InSAR (Model 2), combination of GPS and corrected seafloor measurements (Model 3), combination of GPS and corrected InSAR and seafloor measurements (Model 4), and combination of GPS and initial InSAR and seafloor measurements (Model 5). From the comparison of these slip models, we find combined datasets could give more slip details, which is closer to a joint inversion result constrained from both seismic and geodetic datasets (). RMSE of seafloor measurements has dropped about 4cm after applying postseismic correction. We consider the Model 4, which combines three datasets and takes postseismic correction, to be the preferred solution among all the estimated models. It suggests a maximum slip of 49.87m, located at a depth of 5km around the epicenter, and has a geodetic moment of 3.14×1022 Nm (Mw 8.96) by assuming a shear modulus of 4×1010 Pa. [Copyright &y& Elsevier]

Three-dimensional (3-D) fault geometry and surface slip are key factors for understanding fault behaviour and earthquake mechanics. Previous studies of the 2008 Yutian earthquake occurred on the northwestern Tibetan Plateau, and are limited by a lack of detailed measurements of fault structures and near-fault motion due to the inaccessibility and extreme weather of the area and severe decorrelation of InSAR. In this paper, we use a very-high resolution (VHR) DEM of the 2008 rupture zone extracted from the Pléiades satellite stereo imagery to measure the 3-D fault geometry and on-fault slip. The maximum vertical and horizontal coseismic displacement is 3.6 m and 2.8 m respectively. Despite the overall normal faulting, near-fault reverse vertical motion was observed, ranging from 0.5 m to 1.9 m, caused by the transformation of strike-slip motion into localised shortening due to local fault geometric variations. Measurements of the near-surface dip for the three fault segments (55°, 62°, and 58°) show good consistency, different from previous studies (43°, 60°, and 52°). Joint inversion of InSAR and the near-fault measurements of surface slip also show that the fault geometry does not change much along strike. The local ratio of the cumulative to the coseismic vertical offset recorded on an old alluvial fan and an ice tongue ranges from 1.86 to 2.79, suggesting at least 1–2 historical events occurred here before the 2008 earthquake. • 3D fault geometry and slip of Yutian earthquake from very-high resolution DEM • Near-fault reverse vertical motion caused by local fault geometric variations • Measurements and inversion results show good consistency for dips along strike. [ABSTRACT FROM AUTHOR]

On January 21st, 2016, a Ms 6.4 earthquake hit Menyuan County, Qinghai province, China. The nearest known fault is the Leng Long Ling (LLL) fault which is located approximately 7 km north of the epicenter. This fault has mainly shown sinistral strike-slip movement since the late Quaternary Period. However, the focal mechanism indicates that it is a thrust earthquake, which is different from the well-known strike-slip feature of the LLL fault. In this study, we determined the focal mechanism and primary nodal plane through multi-step inversions in the frequency and time domain by using the broadband regional seismic waveforms recorded by the China Digital Seismic Network (CDSN). Our results show that the rupture duration was short, within 0–2 s after the earthquake, and the rupture expanded upwards along the fault plane. Based on these fault parameters, we then solve for variable slip distribution on the fault plane using the InSAR data. We applied a three-segment fault model to simulate the arc-shaped structure of the northern LLL fault, and obtained a detailed slip distribution on the fault plane. The inversion results show that the maximum slip is 0.43 m, and the average slip angle is 78.8°, with a magnitude of Mw 6.0 and a focal depth of 9.38 km. With the geological structure and the inversion results taken into consideration, it can be suggested that this earthquake was caused by the arc-shaped secondary fault located at the north side of the LLL fault. The secondary fault, together with the LLL fault, forms a normal flower structure. The main LLL fault extends almost vertically into the base rock and the rocks between the two faults form a bulging fault block. Therefore, we infer that this earthquake is the manifestation of a neotectonics movement, in which the bulging fault block is lifted further up under the compresso-shear action caused by the Tibetan Plateau pushing towards the northwest direction. [ABSTRACT FROM AUTHOR]

Regularization is a routine approach used in earthquake slip distribution inversion to avoid numerically abnormal solutions. To date, most slip inversion studies have imposed uniform regularization on all the fault patches. However, adaptive regularization, where each retrieved parameter is regularized differently, has exhibited better performances in other research fields such as image restoration. In this paper, we implement an investigation into adaptive regularization for earthquake slip distribution inversion. It is found that adaptive regularization can achieve a significantly smaller mean square error (MSE) than uniform regularization, if it is set properly. We propose an adaptive regularization method based on weighted total least squares (WTLS). This approach assumes that errors exist in both the regularization matrix and observation, and an iterative algorithm is used to solve the solution. A weight coefficient is used to balance the regularization matrix residual and the observation residual. An experiment using four slip patterns was carried out to validate the proposed method. The results show that the proposed regularization method can derive a smaller MSE than uniform regularization and resolution-based adaptive regularization, and the improvement in MSE is more significant for slip patterns with low-resolution slip patches. In this paper, we apply the proposed regularization method to study the slip distribution of the 2011 Mw 9.0 Tohoku earthquake. The retrieved slip distribution is less smooth and more detailed than the one retrieved with the uniform regularization method, and is closer to the existing slip model from joint inversion of the geodetic and seismic data. [ABSTRACT FROM AUTHOR]

We derived the coseismic and postseismic slip models of the 2011 Van earthquake from multi-source geodetic datasets, including interferometric synthetic aperture radar (InSAR), multi-aperture InSAR (MAI), offset-tracking, and GPS measurements. The constrained least squares algorithm and Laplacian smoothing were used to estimate and regularize the slip distribution. The coseismic slip model suggested two nearly W–E striking segment faults breaking during the Van event. Two main slip concentrations were found to to be located at depths ranging from 7 km to 20 km. The estimated moment reached 6.08 × 10 19 Nm (equal to an Mw 7.19 event). A stress change analysis showed that the main shock imposed an up to ∼5 bars stress load on the causative fault of the 9 November aftershock, implying a triggering mechanism between the two events. The postseismic slips of the Van earthquake were dominated by shallow left-lateral and deep thrust components. The slips distributed in most of the unruptured area of the fault plane. The accumulated postseismic moment reached 2.04 × 10 19 Nm, which was about 34% of the main shock moment. We conclude that the future seismic hazard will be relatively low in this area. [ABSTRACT FROM AUTHOR]

The accuracy of earthquake catalogs limits the reliability of earthquake hazard assessment and the comprehensive understanding of earthquake mechanisms. Current seismic catalogs are based on the inversion of seismic wave data. The accuracy of their source parameters, which reflect the quantity and layout of seismic stations, and the crustal velocity model used, are often highly uncertain. The open source and popularization of Interferometric Synthetic Aperture Radar (InSAR) deformation data offer the potential to provide more accurate source parameters for earthquake catalogs. In this study, we used same-source InSAR data and a consistent processing approach (i.e., the same sampling, inversion algorithm, and processing flow) to obtain the fault slip models and source parameters of 56 earthquakes, covering most of earthquakes observed by the Sentinel-1 since 2014; these were then used to form a unified InSAR earthquake catalog (U-InSAR). We then compiled a second InSAR earthquake catalog (C-InSAR) based on the source parameters of an additional 164 earthquakes inverted using InSAR deformation data from various sources by previous studies, among which 45 earthquakes included additional Global Navigation Satellite System (GNSS) data. The C-InSAR catalog was used to evaluate the impact of data sources and processing approach on the consistency of InSAR catalogs; we found no significant differences between the U- and C-InSAR catalogs. Secondly, the combined U- and C-InSAR catalogs were compared with seismological catalogs, and showed significantly improved seismic source locations, depths, moment magnitudes, fault strikes, fault dips, and fault rakes. Our results confirm the rationality and feasibility of constructing earthquake catalogs using source parameters from a variety of InSAR data sources and inversion algorithms. We emphasize that InSAR catalogs can provide an important supplement, improvement, and/or correction to seismological catalogs, and can provide important basic data for more refined and reliable research on earthquake mechanisms and hazard assessments. Finally, we set up a preliminary sharing and distribution system for InSAR-based catalogs. • Earthquake catalogs were obtained using InSAR data. • U-InSAR comprises same-source InSAR data inverted using the same algorithm. • C-InSAR is comprised of mixed data from previous studies. • U- & C-InSAR have similar accuracy, which is higher than seismological catalogs. • A new InSAR catalog online sharing system provides a range of functions. [ABSTRACT FROM AUTHOR]

Mafic volcanic rocks have erupted in the Tianchi volcanic zone, Changbai Mountains, northeast China, since late Pliocene time. The zone formed in an extensional environment during early-middle Cenozoic time, and in a compressional environment during late Cenozoic. Crustal thickness (about 40 km) in the Changbai Mountains is larger than the regional average of 34–36 km to the northwest and southeast. The conduit for magma upwelling was not coincident with the NE-striking regional faults, but seem to be confined to a deep-seated NW–WNW-striking fault zone. Since the late Pliocene, the Tianchi volcanic zone was subjected to crustal uplift within an intracontinental, weakly compressional environment (with minor WNW–ESE shearing) related to the westward subduction of the West Pacific plate. The nature of this volcanism is not typical of active, subduction-related continental margin volcanism. The magmatic evolutionary process evolved from trachybasalt through basaltic trachyandesite, trachyte, and pantellerite. [Copyright &y& Elsevier]