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The Ganzi‐Yushu fault (GYF) is one of the most seismically active fault systems in eastern Tibet, having experienced five M > 7.0 earthquakes over the past 300 years. Here, we use Sentinel‐1 InSAR data spanning from 2014 to 2023 to derive the interseismic velocity fields along the GYF. We calculate the strain rate fields for the entire fault system, which reveal localized strain accumulation along the GYF as well as along two secondary faults within the Bayan Har block. The inversion results obtained from the elastic block model indicate left‐lateral strike slip rates of 4.0–6.5 mm/yr along the GYF and five locked segments distributed along strike. Furthermore, we identify two shallow creeping segments on the InSAR velocity maps. Based on the locations of the creeping sections and their temporal decay characteristics, we infer that the shallow creep along the GYF is afterslip of the 2010 Yushu earthquake. Plain Language Summary: The 500 km‐long Ganzi‐Yushu fault is a main fault system in eastern Tibet. Investigating its slip behavior is crucial for assessing earthquake potential and understanding the deformation patterns in the region. Using space geodetic observations, we investigate the slip rate distribution along the Ganzi‐Yushu fault. The energy accumulation along the fault can be divided into five segments, which correspond remarkably well with the historical events. Besides the Ganzi‐Yushu fault, we find that two secondary faults within the Bayan Har block, which had not received much attention before, also exhibit significant seismic hazard. We identify two shallow creeping sections along the fault. By analyzing the spatio‐temporal characteristics of the shallow creeping sections, we confirm that they are associated with postseismic activity of the 2010 Yushu earthquake. Our results give insights into the regional deformation mode and seismic hazard. Key Points: Our large‐scale high‐resolution InSAR velocity fields reveal strain accumulation within the Bayan Har blockThere are five locked segments distributed along the Ganzi‐Yushu fault, which corresponds well with historical eventsWe identify two transient shallow creeping segments associated with afterslip of the 2010 Yushu earthquake [ABSTRACT FROM AUTHOR]

SUMMARY: The 2022 Har Lake earthquake sequence, which began in 2022 January and lasted for ∼70 d, jolted the Har Lake area, which is located in the western Qilian Shan, northeastern Tibetan Plateau. Two Mw > 5.5 earthquakes occurred during the earthquake sequence, among which the March 25 Mw 5.8 event is considered the largest event recorded in the area. However, determining the seismogenic faults of the earthquake sequence, as well as the detailed rupture features, is difficult due to the lack of geological data and near-field seismological observations. In this study, we use Sentinel-1 synthetic aperture radar (SAR) data to obtain the coseismic deformation field, identify possible ruptured faults and associated fault geometries, and further estimate detailed coseismic slip models of the two Mw > 5.5 earthquakes. The results show that the January 23 Mw 5.6 earthquake (Earthquake A) occurred on a N15° W-trending dextral-slip fault with a dip angle of ∼61°. For the March 25 Mw 5.8 earthquake (Earthquake B), the interferometric synthetic aperture radar (InSAR) data can be described by either an ∼N–S-trending dextral-slip fault or an ∼E–W-trending sinistral-slip fault. The ∼N–S-trending fault better describes the aftershock distribution, while the ∼E–W-trending model is more consistent with the regional geological setting. We suggest that the complex coseismic ruptures in the multiple-fault system are driven by widespread NE–SW-trending compression in the western Qilian Shan. This study demonstrates the importance of integrating geodetic and seismological observations to capture the full complexity of moderate earthquakes and further suggests potential seismic hazards in the Har Lake area. [ABSTRACT FROM AUTHOR]

Ground surface deformations can be observed during the coseismic and postseismic periods. The accurate determination of displacements is of paramount importance for the assessment of the destructive power of large earthquakes and the characterization of fault behaviors. Therefore, we employ the sub-daily Global Positioning System (GPS) solutions at 19 GPS stations to determine the coseismic and postseismic deformations of the 2010 moment magnitude (Mw) 8.8 Maule earthquake. Using sub-daily GPS data, we can accurately measure both coseismic and early postseismic deformation signals, which can precisely identify the distribution of coseismic slip and the spatiotemporal evolution of early afterslip within the first 36 h. In particular, the sub-daily solution can provide more accurate and quicker results, nearly 10% smaller than those with the daily solution. Furthermore, there is significant ground motion in the immediate postseismic period, which decreases rapidly thereafter. The largest postseismic deformation observed during the first 2 h occurred at station CONZ and amounted to 3.6 cm. During the immediate postseismic period of the 2010 Maule earthquake, afterslip is the dominant mechanism, while poroelasticity plays a negligible role within the first 36 h. Meanwhile, early aftershocks tend to occur in the boundary and the inner part of the afterslip, indicating that the afterslip has the potential to drive the occurrence of aftershocks in the initial stages of postseismic activity. [ABSTRACT FROM AUTHOR]

Previous studies have shown that it is difficult to determine whether the 2015 Pishan earthquake occurred on a uniform fault or a ramp-flat fault with variable dip angles due to the similar goodness of data fit to coseismic and afterslip models on these two fault models. Here, we first present the InSAR deformation obtained from both ascending and descending orbits, covering the coseismic period and cumulative 5-yr period after the 2015 Pishan earthquake. We then determine the preferred fault geometry by the spatial distributions between the positive Coulomb failure stress change triggered by main shock and the afterslip. Based on the preferred fault model, we finally use a combined model to determine the contributions of elastic and viscoelastic deformation in the post-seismic deformation. We find that the Pishan earthquake prefers to occur on a ramp-flat fault, and the coseismic slip is mainly distributed at a depth of 9–13 km, with a maximum slip of about 1.3 m. The post-seismic deformation is primarily governed by afterslip, as the poroelastic rebound-induced deformation fails to account for the observed post-seismic deformation and the contributions from the viscoelastic relaxation mechanism can be considered negligible in the combined model. Moreover, the modelled stress-driven afterslip and observed kinematic afterslip have good consistency, and the difference between the root mean square error of the two afterslip models is only 4.3 mm. The results from the afterslip model indicate that both of the updip and downdip directions distribute the afterslip, and slip in the updip direction is greater than that of the downdip direction. Meanwhile, the maximum cumulative afterslip after 5 yr is approximately 0.26 m which is equivalent to a released seismic moment of a M w 6.47. [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]

On 2015 November 4, an M w 6.5 earthquake struck the east region of Alor Island, eastern Indonesia. Here, we use Sentinel-1 and ALOS-2 data to explore the coseismic surface displacement of this earthquake. Based on the ALOS-2 coseismic interferograms, the first fault model and coseismic slip distribution of the 2015 Alor earthquake are presented in this study. The preferred slip model links to a blind south-southeast striking, south-southwest dipping strike-slip fault with amount of normal slip component and a peak slip of 2.09 m at 2.34 km of depth. Considering the fact that the ascending and descending InSAR prediction of the distributed slip model does not fit the InSAR observations at the northwest and southeast tips with the simple planar fault model. We tried to construct a strike-variable fault model to further improve data fit. The results of the calculated Coulomb stress change imply that the regions with positive CFS changes mainly located at the northwest and southeast extremities of the rupture of the Alor earthquake, and in the lobes north and south of the rupture. The most striking discovery from the InSAR observations of the Alor earthquake is that most of the displacements occurred on a fault whose existence was unknown before the earthquake. [ABSTRACT FROM AUTHOR]

To resolve the occurrence mechanism of the Luxian earthquake occurred near an active hydraulic fracturing well pad on 15 September 2021, we first use seismic waveforms to invert the focal mechanism solution and centroid depth, and then utilize Sentinel‐1 Synthetic Aperture Radar images and Global Navigation Satellite System observations to determine the seismogenic fault and slip distribution. Our results show that the Luxian event ruptured a previously‐unmapped southwest‐dipping reverse fault intersecting with one horizontal well of the well pad. Major slip occurred below the shale gas bed (∼4 km deep) but above the crystalline basement (∼7 km deep). Further analyses on preseismic surface deformation initiated in the northeast of the event reveal that pore pressure near the hypocenter was increased by ∼4.5 MPa. Consequently, fracking fluid injected through the horizontal well and other wells of nearby pads likely flowed directly into the fault zones and prompted the occurrence of the Luxian earthquake. Plain Language Summary: Due to huge casualties and property losses, the Ms 6.0 Luxian earthquake aroused wide public concern. Beyond that, at 0.85 km south of the epicenter, there is a hydraulic fracturing (HF) well pad (H79) that was operating before the earthquake occurrence. Therefore, people suspect that there was some relationship between the event and HF operations. We here jointly use seismic waveforms of regional permanent stations, Sentinel‐1 Synthetic Aperture Radar images, and Global Navigation Satellite System observations to determine the location and 3D geometry of the source fault. We find the fault intersecting with one horizontal well of the nearby pad, indicating that fracking fluid can flow directly into the fault zones and cause pressure perturbation with magnitudes comparable to the minimum principal stress. In addition, we also find preseismic deformation around the epicenter initiated after 29 May 2021. The deformation is likely linked to accumulation of fracking fluid injected during the drilling and HF operations of other pads. Further modeling reveals that the fluid accumulation increased pore pressure by ∼4.5 MPa near the hypocenter. The source fault likely suffered pressure diffusion before the operation of well pad H79 and was eventually reactivated by pressurization directly linked to HF stimulation. Key Points: The Luxian earthquake ruptured an unmapped south‐dipping reverse fault with major slip occurred in deep sedimentary formationsPreseismic surface deformation analyses indicate that fracking fluid accumulation likely caused pressure increase near the hypocenterThe source fault, intersecting with one horizontal hydraulic fracturing well, was likely reactivated by direct fault‐zone pressurization [ABSTRACT FROM AUTHOR]

A devasting Mw7.2 earthquake struck southern Haiti on 14 August 2021, leading to over 2000 casualties and severe structural failures. This earthquake, which ruptured ~70 km west of the 2010 Mw7.0 event, offers a rare opportunity to probe the mechanical properties of southern Haiti. This study investigates the kinematic multi-fault coseismic rupture process by jointly analyzing teleseismic and interferometric synthetic aperture radar (InSAR) datasets. We determined the optimal dip of different segment faults through finite-fault inversion, and the results show that the dips of the first, second and third faults are 62°, 76° and 76°, respectively, coinciding with the relocated aftershock distribution. The results estimated from our joint inversion revealed that the slip was dominated by reverse motion in the first segment and strike-slip motion in the second and third segments. Three slip patches were detected along the strike, with a peak slip of 3.0 m, and the rupture reached the surface at the second segment. The kinematic rupture process shows a unilateral rupture with a high centroid rupture velocity (5.5 km/s), and the rupture broke through the stepover and caused a cascade rupture. The rupture front experiences a directivity pulse of high ground motions with high amplitude and short duration, which may be an additional factor explaining the many landslides concentrated on the western end of the fault. The Coulomb failure stress change result indicates the increases in the probability of future events to the east and west of the 2021 main shock. [ABSTRACT FROM AUTHOR]

On 23 January and 25 March 2022, two MW > 5.5 Hala Lake earthquakes characterized by right-lateral strike-slip faulting occurred around the Elashan Fault in Northeastern Tibet, marking the two largest events since the 1927 MW 6.2 Hala Lake earthquake. Since no surface rupture related to the two earthquakes has been reported, the seismogenic faults and coseismic rupture behaviors of the two events are still unknown. The occurrence of the two events provides a rare opportunity to gain insight into the seismogenic structure and rupture behavior of the less studied region, further helping us accurately evaluate the regional seismic hazard. Here, we first exploit Interferometric synthetic aperture radar (InSAR) data to obtain the coseismic deformation associated with the two earthquakes and then invert for the fault geometry and detailed coseismic slip of the two events. Coseismic modeling reveals that the January and March 2022 earthquakes ruptured two buried west-dipping moderate-angle and high-angle right-lateral strike-slip faults, respectively. Most of the slip of the January event occurred at depths from 1.7–7.6 km, while the majority of the slip associated with the March event occurred at depths from 2.5–10 km, which may have been restricted by the intersections between the January and March Hala Lake seismogenic faults. By a comprehensive analysis of the coseismic inversions, stress changes, and early postseismic signal, we suggest that the significant fault dip difference (~30°), highlighting a fault segmentation, stops the rupture propagation from one fault segment to another and that fluid migration may encourage the restart of the rupture of the later event, which requires further investigation. Moreover, Coulomb stress modeling shows stress loading on the eastern segment of the Daxueshan–Shule Fault and the northern segment of the Elashan fault, which we should pay more attention to. [ABSTRACT FROM AUTHOR]

On 7 January 2022, a Mw 6.6 earthquake struck Menyuan County in the Qinghai province of China and the earthquake caused severe damage to infrastructures. In this study, the performance of the high-rate global navigation satellite system (GNSS) on real-time source modeling of the 2022 Mw 6.6 Menyuan earthquake was validated. We conducted the warning magnitude calculation, centroid moment tensor (CMT) inversion, and static fault slip distribution inversion using displacements collected from 14 1-Hz GNSS stations. Our results indicate that the warning magnitude derived from the peak ground displacement (PGD) first exceeds Mw 6.0 approximately 9 s after the earthquake and tends to be stable after about 45 s. The derived finally stable magnitude is Mw 6.5, which is near the USGS magnitude of Mw 6.6. Based on the inverted CMT and static fault slip distribution results, it can be determined that the 2022 Menyuan earthquake is a left-lateral strike-slip event after about 20 s of the earthquake. Although the fault slips, inverted with the 30-s smoothed coseismic offsets, are unstable after about 40 s, all the inverted slip models after that time present the obvious surface rupture and the most fault motions are concentrated between the depth of 0 km and 8 km. Compared with the results inverted with the 30-s smoothed coseismic offsets, the CMT and fault slips inverted with the 70-s smoothed coseismic offsets are more stable. The results obtained in this study indicate that the high-rate GNSS has the potential to be used for real-time source modeling for earthquakes with a magnitude less than 7; the stability of the inverted CMT and fault slips can be improved by using the coseismic offsets averaged by a relatively long-time sliding window. [ABSTRACT FROM AUTHOR]

On May 21, 2021, a Mw 7.4 earthquake struck the Maduo County in Qinghai province of China. The earthquake was well recorded by the surrounding high-rate Global Navigation Satellite System (GNSS) stations. In addition to GPS, GLONASS and BDS2 observations, these stations also recorded the latest BDS3 and Galileo observations. The performance of high-rate single-GNSS and fusion of multi-GNSS on warning magnitude calculation, rapid centroid moment tensor inversion and static fault slip inversion are well investigated in this study. The results demonstrate that within a short period of time (5 min), Precise Point Positioning (PPP) displacements of BDS3 alone are better than those of BDS2 alone, while the individual displacement accuracies of BDS3, GPS and Galileo are comparable. When BDS3 and BDS2 data are combined, the combined BDS accuracy is slightly better than that of GPS or Galileo alone. Compared with the single-GNSS displacements, the fusion of GPS + GLONASS + Galileo + BDS3/2 (GREC) can achieve the highest accuracy with standard deviation values of 0.25 cm, 0.22 cm and 0.53 cm in north, east and up components, respectively. For the warning magnitude estimation, BDS3 alone, BDS2 alone, combined BDS3/2, combined GPS + BDS3/2, Galileo alone and GREC all show comparable performance. The results of centroid moment tensor inversion and static fault slip inversion are related to the station distribution. When the same stations are used, the inverted centroid moment tensors and static fault slips of a single GNSS are very similar to the multi-GNSS inversion results, but the multi-GNSS centroid moment tensor series and fault slips appear to be more stable when the observation quality of a single GNSS such as GLONASS, is relatively low. The results obtained in this study imply that GPS, BDS3, Galileo and combined multi-GNSS have the potential to be used for the earthquake early warning and rapid earthquake source modeling. [ABSTRACT FROM AUTHOR]

The 2019 Ridgecrest earthquake sequence in the Mojave Desert that ruptured a complex orthogonal conjugate fault system offers a rare opportunity to probe the mechanics of the intraplate lithosphere of the central eastern California shear zone (ECSZ). We used space geodetic data to investigate the coseismic and post-seismic deformations attributable to this earthquake sequence. A triangular dislocation inversion scheme was used to derive the coseismic and post-seismic slip distributions on five non-planar faults in a homogeneous elastic crust. A wide range of viscoelastic relaxation models with varying upper mantle viscosities were also tested to constrain the rheological structure. The inferred coseismic slip exhibited a pronounced (approximately 60 per cent) shallow slip deficit (SSD), only a small proportion of which was recovered by early aseismic afterslip. Inversions of GPS and InSAR data suggest that the near-field post-seismic transient was dominated by afterslip at depths of 3–8 km. Viscosity modelling yielded a robust lower bound of approximately 8.0 × 1017 Pa s on the viscosity of the upper mantle. Both the GPS observations and the modelled viscosity at each individual station showed a lateral heterogeneous relaxation process on both northeast and southwest ECSZ. The effective viscosity of the mantle asthenosphere to the northeast was inferred to be approximately two times lower than that to the southwest, which is consistent with the pattern expected for regional heat flow. A comparison among the static coseismically induced Coulomb stress changes, the cumulative distribution of aftershocks and the afterslip distribution suggests that aftershocks and shallow afterslip could be responses to coseismically induced stresses, but the aftershock and afterslip distribution are poorly correlated. We argue that the pronounced SSD and lack of shallow afterslip during the Ridgecrest earthquake sequence are indicative of an immature fault. Furthermore, we suggest similar rheological structures for the southern and central ECSZ and infer a relatively low effective viscosity for the mantle to the northeast because of its high heat flow. We also propose that the afterslip may illuminate the rate-strengthening regions that mostly slip aseismically, but the aftershocks may illuminate fluid-saturated areas near ruptures. [ABSTRACT FROM AUTHOR]

Three Mw > 5.5 earthquakes (Tyrnavos, Elassona and Verdikoussa earthquakes) struck the northern Thessaly, Greece, from 3 March to 12 March 2021, filling a significant seismic gap. We exploit Interferometric synthetic aperture radar data to investigate coseismic deformation of these events and the first half‐year postseismic deformation related to the Tyrnavos event. Our coseismic modeling reveals that the seismic sequence activated at least four unmapped low‐angle normal faults. However, postseismic analysis shows that afterslip propagates updip to a high‐angle shallow structure, indicating that the coseismic slip and afterslip jointly activated a ramp‐flat structure. By a comprehensive analysis of the inversions, fault distribution, relocated aftershocks and regional stress changes, we highlight that intersections between the main and secondary faults control the slip extent and rupture termination in each earthquake and that static stress transfers induced by earlier event encourage the rupture reinitiation of the later event. Plain Language Summary: As the largest events to hit the Tyrnavos basin since 1941 Mw 6.3 Larissa earthquake, the Thessaly seismic sequence consisting of three Mw > 5.5 earthquakes provides a rare chance to gain insight into the regional seismogenic structure as well as the rupture behavior of faults. Here, we combine coseismic Interferometric synthetic aperture radar observations and relocated aftershocks to explore the optimal seismogenic structure of the seismic sequence which ruptured at least four buried normal faults: one NE‐dipping main fault and one NNE‐dipping secondary fault for the Tyrnavos event, one NE‐dipping fault for the Elassona event and one antithetic SW‐dipping fault for Verdikoussa event. Further combined with an analysis of field investigation and postseismic observations following the Tyrnavos event, we find compared with coseismic slip at depths of 1.9–8.4 km on a gentle main fault, most afterslip is confined at depths of 0–1.7 km on a steep fault, which reveals a ramp‐flat structure. We further investigate the causes for cascading (stop‐start) rupture of the seismic sequence and find that fault intersections play a significant role in halting the rupture propagation, leading to a multi‐fault delayed rupture, and that static stress changes promote the restart of slip. Key Points: Coseismic deformation of the 2021 Thessaly seismic sequence and postseismic deformation following the mainshock are measured with Interferometric synthetic aperture radarAt least one ramp‐flat normal fault and three planar normal faults are activated during the 2021 earthquake sequenceIntersections between the main and secondary faults control the rupture propagation in each earthquake [ABSTRACT FROM AUTHOR]

Mixture density networks (MDNs) are a class of neural network algorithms in the Bayesian framework that can invert for parameters and estimate the parameter uncertainties at the same time. We test MDNs by inverting the fault geometric parameters in a synthetic test with Okada's model and demonstrate the efficiency and robustness of the model. To further describe the MDNs algorithm, we invert regional static GPS displacement data for the 2013 Ms7.0 Lushan Earthquake in China to obtain the fault geometric parameters. The inverted geometric parameters, which are in the form of distributions, agree well with the published solutions for this event once the 99.7% confidence interval are taken into account. The 99.7% confidence intervals of the strike and dip angles are [ 187. 5 ∘ , 220. 4 ∘ ] and [ 20. 76 ∘ , 49. 76 ∘ ], respectively. To demonstrate the applicability of the inverted geometric parameters, we invert the slip distribution of the Lushan earthquake with the inverted parameters and GPS displacements. From the slip distributions considering the distributions of the parameters, we obtain the 99.7% confidence intervals of the magnitude Mw, maximum slip and depth of maximum slip, which are [6.51, 6.65], [0.30, 0.74] m and [9.43, 13.61] km, respectively. [ABSTRACT FROM AUTHOR]

We use mainly geodetic observations to constrain the fault geometry and coseismic distribution of the 2018 Kaktovik earthquake sequence, Alaska. We find that at least three faults were activated. The earthquake sequence ruptured mainly an ESE‐striking, SSW‐dipping strike‐slip fault and a secondary rupture on an SE‐striking, SW‐dipping normal fault. Slip also occurred on a small SSW‐striking fault plane, which is found first in geodetic data and further verified with geological data and focal mechanism solutions. We also map 6 months of postseismic deformation and find obvious displacements in the center of the Sadlerochit Mountains. A geological model is proposed to interpret the relationship between this earthquake sequence and the regional structure. We suggest that the 2018 Kaktovik earthquake sequence may first have occurred on a fault unknown prior to the mainshock and triggered slip on both the pre‐existing ramp structure below the Sadlerochit Mountains and a secondary structure. Plain Language Summary: The 2018 Kaktovik event is the largest earthquake ever to be reported and recorded within the eastern Brooks Range and presents an unprecedented opportunity to study the regional tectonic structure and crustal deformation. Here, we present a detailed investigation into the seismogenic structure of this earthquake sequence, which ruptured mainly an ESE‐striking, SSW‐dipping strike‐slip fault and a secondary SE‐striking, SW‐dipping normal fault. Slip also occurred on a small SSW‐striking fault plane, which is found first in the geodetic data and further verified with seismic and geological data. Perhaps the most striking discovery from the InSAR observations of the Kaktovik earthquake sequence is that most of the displacement occurred on a fault whose existence was unknown prior to the earthquake sequence: a blind fault with no surface expression; additionally, a conjugate fault structure could have been triggered in this earthquake sequence. To explain the different orientations and kinematics of the two main ruptures (Faults 1 and 2), we use a ramp structure with variable geometry for the main fault zone: The first rupture has a higher dip and more strike‐slip, while the second rupture has a lower dip and a dominant normal component. Key Points: The coseismic deformation of the 2018 Kaktovik earthquake sequence is derived from Sentinel‐1 imagesLarge along‐strike variations in the coseismic deformation highlight the complexity of the ruptureWe propose a geological model to connect this earthquake sequence with the regional structure [ABSTRACT FROM AUTHOR]

The 2019 M w 7.1 Ridgecrest earthquake opens an opportunity to investigate how soon we can produce a reliable fault geometry and subsequently a robust source model based on high-rate Global Positioning System (GPS) data. In this study, we conduct peak ground displacement (PGD) magnitude scaling, real-time centroid moment tensor (CMT) calculation and rapid kinematic slip inversion. We conclude that a four-station PGD warning with a magnitude of M w 7.03 can be issued at 24 s after initiation of the rupture. Fast CMT inversion can initially recover the correct nodal planes at 30 s. The kinematic slip model reveals that the M w 7.1 earthquake is a predominant dextral strike-slip event with both normal and thrust components resolved. The earthquake shows a bilateral rupture with a low propagation speed of ∼2.1 km s−1 and a slip maxima of ∼4 m. The total moment is 5.18 × 1019 N m (M w 7.11). We further suggest that a reasonable source model will be available in a simulated real-time mode within 30 s after the earthquake occurring, without using full high-rate GPS waveforms. This research highlights the significance of high-rate GPS for rapid earthquake response and modelling of kinematic rupture, which is also generalized by the hypothetical real-time GPS analysis for the 2016 M w 7.8 Kaikoura earthquake and the 2010 M w 7.2 El Mayor-Cucapah earthquake. [ABSTRACT FROM AUTHOR]

Although the Papuan fold and thrust belt (PFTB) is thought to accommodate convergence between the Pacific and Australian plates, the possible strain partitioning and its kinematic controls in the region are poorly understood. On 25 February 2018, a devastating Mw 7.5 earthquake jolted the southern area of the PFTB, central Papua New Guinea. The detailed imaging of the source parameters of this large earthquake is an urgent demand for a better understanding of the tectonism in the region. Here we used spaceborne interferometric synthetic aperture radar data to carefully determine the possible ruptured faults and associated fault geometries and further estimated the detailed slip of the 2018 Mw 7.5 earthquake. We find that the earthquake involved multiple faults failure, and a four‐segment fault model can reasonably produce the complex coseismic deformation, especially the observed bimodal displacements. The earthquake was dominated by reverse fault motion, and significant slip of up to ~0.7 m was documented on faults extending at depths great than 25 km. An integrated analysis of the fracture complexities suggests that possible strain partitioning in the PFTB could be tightly coupled with regional fault geometries and lithospheric properties. Our findings on the deep brittle failures suggest that crustal shortening across the PFTB could primarily control the growth of fold and thrust belt in the central Papua New Guinea. Key Points: Complete coseismic surface deformation generated from InSAR helps determine ruptured faults and constrain the complex source parametersThe 2018 Mw 7.5 Papua New Guinea earthquake was characterized by deep‐seated reverse faulting with ruptures extending into depths of 25 kmThis event revealed the possible strain partitioning in the Papuan fold and thrust belt and can help explain its growth [ABSTRACT FROM AUTHOR]

In traditional tight integration of high-rate GNSS and strong motion sensors, an appropriate process variance is crucial for obtaining accurate broad-band coseismic deformations. In this paper, instead of using a subjectively empirical value, we present an approach for determining the process variance adaptively based on the adaptive Kalman filter for real-time use. The performance of the approach was validated by the colocated stations collected during the 2010 M w 7.2 earthquake in El-Mayor, 2016 M w 7.8 earthquake in New Zealand and 2016 M w 6.5 earthquake in central Italy. The results show that this method complements the advantages of GNSS and strong motion accelerometers and can provide more accurate coseismic waveforms especially during the strong shaking period, due to the ability of the method to adjust the process variance in real time according to the actual status of the station. In addition, this method is also free from the influence of the baseline shift. Testing of the new method for the integration of strong motion and multi-GNSS indicates that multi-GNSS has an obvious improvement in the precision while single GPS has a poor observation condition. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Small amplitude deformation due to a range front earthquake is detected from the SAR data. • Source parameters inversion shows that this earthquake is a blind thrust event. • Multiple-source data lead support that this earthquake occurred on a back-thrust of the HMT fault. Abstract The Tian Shan Range, which trends E-W along the southern margin of the Junggar Basin, is one of the longest and most active intracontinental orogenic belts in central Asia. On 8 December 2016 (05:15:04 UTC), a Mw 6.0 earthquake ruptured the northern Tian Shan front. Here, we use Sentinel-1 radar imagery to investigate the deformation and source parameters related to this event. The co-seismic surface deformation was predominated by uplift without surface rupture. Ascending and descending interferograms indicate that the event triggered small co-seismic deformations with maximum line-of-sight displacements of 22 mm and 24 mm, respectively. Although the north-dipping and south-dipping plane solutions can both fit the observations well, the north-dipping solution with a dip of 58° is preferred in consideration of the relocated aftershocks and regional geological structure. Significant slip is located between depths of 12 km and 17 km, suggesting that the event was caused by a completely blind thrust fault. This blind rupture is characterized largely by a compact thrusting patch with a peak slip of 56 cm at a depth of 13 km. The source model generates a geodetic moment of 6.678 × 1017 N m corresponding to a Mw 5.85 event. Both the interferometric synthetic aperture radar modeling and the aftershock locations indicate that the rupture plane is linked to the Huoerguosi-Manas-Tugulu fault at a depth of ∼16 km, a typical locking depth in the Tian Shan. We suggest that the 2016 Hutubi earthquake more likely occurred on a back-thrust of the Huoerguosi-Manas-Tugulu fault, and the back-thrust is interpreted to represent a preexisting normal fault beneath the Qigu anticline belt that was tectonically inverted during the Cenozoic. [ABSTRACT FROM AUTHOR]

We use Sentinel‐1 radar imagery to explore the coseismic and postseismic surface displacements associated with the 2016 MW 6.2 Lampa earthquake in southern Peru. Based on coseismic interferograms, the preferred slip model links to a blind south southeast striking, south southwest dipping normal fault with a shallow dip (45.2°) and a peak slip of 0.71 m at depth ~5.3 km, which is consistent with seismic solutions. Postseismic interferograms, derived from two tracks of the Sentinel‐1A/B satellites using a small baseline subset method, show subsidence up to ~3 cm in the first year after the mainshock. The kinematic inversions of interferometric synthetic aperture radar (InSAR) observations imply that the postseismic surface displacements observed in 1 year after the earthquake are governed by afterslip occurring along the updip extension of the coseismic slip patches. To further improve the data fitting, we generate a fault with variable strike to refine the kinematic afterslip model. The stress‐driven afterslip forward modeling shows that the postseismic deformation is controlled by afterslip distributed at the edge of the compact coseismic slip area. The surface displacement predictions of the poroelastic rebound show subsidence of the hanging wall, but the magnitude of the displacements is small compared to the observed signal. We as well test a collection of viscoelastic relaxation models and find that the predicted surface displacements are not consistent with the observations. The InSAR results show that the strike of the seismogenic fault is quasi‐parallel to the Vilcanota normal fault system and both the fault associated with earthquake and Vilcanota normal fault dip in the same direction. Therefore, we suspect that the causative fault of this 2016 event may be a normal fault belonging to a "domino" faulting system. Key Points: Coseismic and postseismic deformation of the 2016 Lampa earthquake were derived from the InSAR observationsThe inversion results suggest that the seismogenic fault of the Lampa earthquake is a blind, southwest dipping normal faultInSAR time series analysis that shows postseismic deformation of the Lampa earthquake mainly locates just updip of the coseismic rupture [ABSTRACT FROM AUTHOR]

Mapping the three-dimensional (3D) displacement fields associated with a variety of geological phenomena has been widely performed by exploiting synthetic aperture radar (SAR) imagery, as the result is important for providing insight into the formation mechanisms and potential risks of geological hazards. New-generation SAR sensors, namely ALOS-2 and Sentinel-1, can capture surface deformation with a high coherence in wide-swath mode, thereby providing outstanding across-track displacement accuracies; however, this improvement partially sacrifices the azimuth resolution, which affects the retrieval of 3D surface deformation fields. To explore the feasibility of generating 3D deformation maps with new SAR imagery, we collect two pairs of ALOS-2 ScanSAR and four pairs of Sentinel-1 Terrain Observation by Progressive Scans (TOPS) images for the 12 November 2017 Ezgeleh earthquake. Furthermore, the differential interferometric SAR (DInSAR), pixel offset tracking (POT), multiple-aperture InSAR (MAI), and burst-overlap interferometry (BOI) methods are used to measure the across- and along-track displacements. Compared with the POT and MAI methods, the integration of DInSAR and BOI measurements provides high-quality 3D deformation maps with an accuracy of 4 cm, which is four times and two times better than the accuracies of the POT and MAI methods integrated with DInSAR, respectively. In addition, a significant north-south displacement of 0.76 m is found in our 3D deformation results that was underestimated in the slip distribution model constrained with seismic waveforms or InSAR measurements. Our 3D deformation map of the 2017 Ezgeleh earthquake indicates a southwestward horizontal motion and an upward motion without any corresponding surface rupture that effectively match the behavior of a blind rupture along a northeast-dipping reverse fault. We conclude that combining BOI with DInSAR would provide a better 3D deformation field and should be applied to study future earthquakes. [ABSTRACT FROM AUTHOR]

The mechanisms of unusual shallow intraplate earthquakes that occasionally occur in stable cratons remain poorly understood. Here we analyze coseismic and postseismic displacement fields associated with the 2016 Petermann Ranges earthquake in central Australia using interferometric synthetic aperture radar data. The earthquake ruptured a previously unmapped fault and was dominated by thrust slip motion of up to 95 cm within the top 3 km of the crust. Postseismic deformation analysis suggests that a combination of poroelastic rebound and afterslip are responsible for the observed signals. The inferred afterslip overlapping spatially with the coseismic rupture highlights that the postseismic slip is coupled with the pore fluid flow around the fault zones. Analysis of historic groundwater‐level changes suggests that shallow seismicity around the Petermann Ranges may have been triggered by environmental stress perturbations due to the fluctuations of groundwater level; however, it is not easy to document statistical significance of this correlation. Plain Language Summary: Shallow surface‐rupturing earthquakes have been observed globally. However, how these events are triggered and why they sometimes occur within stable continents is largely unknown. We carefully study the coseismic and postseismic deformation of a 2016 Mw 6 earthquake in central Australia to determine the source parameters and slip distributions. We find the coseismic slip and early afterslip are concentrated at depths shallower than 3 km, and poroelastic rebound substantially contributes to the early period of postseismic deformation. We further investigate potential mechanisms to explain rock failure at such shallow depth and find a possible relationship between the fluctuations of groundwater level and the occurrence of shallow seismicity in the region. The results of this study help shed light on the processes and causes of shallow earthquakes. Key Points: Coseismic slip of the 2016 Mw 6 Petermann Ranges earthquake is concentrated at shallow depths between 0 and 3 kmPostseismic displacements are governed by a combination of poroelastic rebound and afterslipThe occurrence of shallow earthquakes might be caused by groundwater levels changes in central Australia [ABSTRACT FROM AUTHOR]

In 2016, the Mw 5.9 Menyuan earthquake occurred at the western end of the Tianzhu seismic gap in the middle segment of the left-lateral strike-slip Haiyuan fault system. Studying the focal mechanism of the Menyuan earthquake and its correlation with historical seismicity is of great significance in understanding the tectonic style of the Haiyuan fault system and assessing the Tianzhu gap seismic risk. Using Sentinel-1A radar imagery, we obtain the coseismic deformation field of the Menyuan earthquake in the LOS direction and invert the deformation field slip distribution model. Based on the interseismic deformation field reflected by GPS data and the relocated results of aftershocks provided by previous studies, we then analyze the seismogenic nodal plane of the Menyuan earthquake and consider the west-dipping model to be the most likely seismogenic solution. The west-dipping model indicates that the average slip of the Menyuan earthquake is 0.41 m, and the average rake angle is 68°, with a magnitude of Mw 5.905. Considering the historical strong earthquakes and viscoelastic layered crust, the results from Coulomb failure stress modeling indicate that the Coulomb stress loading caused by the historical strong events promoted the occurrence of the 2016 Menyuan earthquake. Both the low seismicity within the Tianzhu gap and the cluster phenomenon of medium earthquakes on the Lao Hu Shan (LHS) and Leng Long Ling (LLL) faults have strong correlations with the stress change distribution resulting from the historical strong earthquakes. A series of medium events occurring on the north side of the LLL fault, represented by the 2016 Menyuan earthquake, would raise the seismic risk on the western end of the Tianzhu gap. [ABSTRACT FROM AUTHOR]

The 7 January 2022 M w 6.6 Menyuan earthquake struck the Qilian-Haiyuan fault zone, NE Tibet, offering a chance for understanding the regional seismogenic structure and rupture behavior. We use Interferometric synthetic aperture radar data to study the coseismic and early postseismic deformation of the event. Coseismic modelling highlights that the earthquake activated two strike-variable high-angle strike-slip faults (one SE-trending main fault and one ENE-striking secondary fault) corresponding to only part of the Lenglongling and Tuolaishan faults. Further postseismic analysis not only reveals a localized postseismic signal of up to ∼3 cm related to the mainshock but identifies an obvious coseismic signal of up to ∼2.3 cm associated with an M W 5.1 aftershock characterized by sinistral strike-slip-faulting. The 2022 Menyuan earthquake, large aftershock and 2016 M w 5.9 thrust-faulting Menyuan earthquake illuminate a positive flower structure of the Lenglongling fault. By a joint analysis of the inversions, fault kinematics and historical earthquake, we suggest that fault branches and low pre-stress jointly restrain the maximum rupture size in the 2022 Menyuan event. • Coseismic deformation of 2022 Menyuan earthquake and its largest aftershock and postseismic deformation of mainshock are detected with InSAR. • Two strike-variable strike-slip faults with different dips are activated during the 2022 Menyuan earthquake. • Fault branches and low pre-stress may jointly limit the lateral slip propagation in the 2022 Menyuan earthquake. [ABSTRACT FROM AUTHOR]

Highlights • Coseismic deformation is derived from near-field GPS measurements and InSAR interferograms. • A planar fault model explains the coseismic deformation better in comparison to a listric fault model. • The slip distribution is characterized by two separate asperities on a steeply-dipping planar fault. • The recurrence interval of the 2016 Mw 6.7 Aketao earthquake is deduced to be 100–230 years. Abstract On 25 November 2016, the Aketao, Xinjiang earthquake occurred on the Muji fault, which is located at the northernmost end of the right-lateral Karakorum Fault (KF). This event provides a rare chance to gain insights into how the stress accumulates in Pamir margin as the Indian plate collides with the Eurasian plate. Space geodetic measurements including InSAR and GPS were used to obtain coseismic surface displacements associated with this earthquake. Based on a finite fault model, the coseismic slip distribution inverted by the combined datasets indicates that the 2016 Aketao event is caused by a primary shallow strike-slip with minor normal-slip at a steep-dipping angle. To explore the real structure of Muji fault, listric fault model inferred by relocated aftershocks as well as the planar fault model, were used in our slip distribution inversion. The results suggest that the optimal fault model should be a highly-dipping planar fault with two separated asperities. The large slip zone is beneath the surface near the epicenter with a maximum slip of 1.1 m, while the small one in the east breaks the surface, in a good agreement with the field seismic geological survey. The total geodetic moment is 1.35 × 1019 N∙m , equivalent to Mw 6.7. The nearly pure dextral strike-slip Aketao earthquake, and the recent 2015 Mw 7.2 sinistral strike-slip Tajikstan earthquake in this region, to some extent, manifest the extension motion is dominated in northern Pamir Plateau, in response to the northward convergence between Indian and Eurasian collision. [ABSTRACT FROM AUTHOR]

Twelve Sentinel-1 images are used to measure the surface displacements caused by the Zaduo earthquake on 17 October 2016 in Qinghai, China. Comprehensive analysis of the local geologic structure, focal mechanisms, relocated aftershocks, and fault geometrical parameters from nonlinear inversions of the InSAR data indicates that a NE-trending fault with a strike of ~ 61°, namely the Aduo fault, was responsible for this event. Further geodetic inversions for finite fault models show that the dip angle of this fault is 75° to the SE. The majority of the slip occurred at the depth from 5 km to 17 km, and the normal-slip component was comparable to the strike-slip component. The peak slip of ~ 31 cm occurred at a depth of ~ 10 km. The InSAR determined moment is 9.61 × 1017 N m with a rigidity of 30 GPa, equivalent to Mw 5.9. The geological map reveals that the Aduo fault was characterized by a left-lateral strike-slip component in the past, as evidenced by the offset of Paleogene sedimentary rocks. Our results for the Zaduo earthquake suggest that the Qiangtang block probably consists of two or more sub-blocks with different eastward extrusion velocities and that the deformation of the Qiangtang block is occurring not only along its boundaries but also in its interior. [ABSTRACT FROM AUTHOR]

New satellites are now revealing InSAR-based surface deformation within a week after natural hazard events. Quick hazard responses will be more publically accessible and provide information to responding agencies. Here we used Sentinel-1 interferometric synthetic aperture radar (InSAR) data to investigate coseismic deformation associated with the 2017 Sangsefid earthquake, which occurred in the southeast margin of the Kopeh Dagh fault system. The ascending and descending interferograms indicate thrust-dominated slip, with the maximum line-of-sight displacement of 10.5 and 13.7 cm, respectively. The detailed slip-distribution of the 2017 Sangsefid Mw6.1 earthquake inferred from geodetic data is presented here for the first time. Although the InSAR interferograms themselves do not uniquely constrain what the primary slip surface is, we infer that the source fault dips to southwest by analyzing the 2.5 D displacement field decomposed from the InSAR observations. The determined uniform slip fault model shows that the dip angle of the seimogenic fault is approximately 40°, with a strike of 120° except for a narrower fault width than that predicted by the empirical scaling law. We suggest that geometric complexities near the Kopeh Dagh fault system obstruct the rupture propagation, resulting in high slip occurred within a small area and much higher stress drop than global estimates. The InSAR-determined moment is 1.71 × 10 18  Nm with a shear modulus of 3.32 × 10 10  N/m 2 , equivalent to Mw 6.12, which is consistent with seismological results. The finite fault model (the west-dipping fault plane) reveals that the peak slip of 0.90 m occurred at a depth of 6.3 km, with substantial slip at a depth of 4–10 km and a near-uniform slip of 0.1 m at a depth of 0–2.5 km. We suggest that the Sangsefid earthquake occurred on an unknown blind reverse fault dipping southwest, which can also be recognised through observing the long-term surface effects due to the existence of the blind fault. [ABSTRACT FROM AUTHOR]

The 2016 Ecuador earthquake ruptured the Ecuador-Colombia subduction interface where several historic megathrust earthquakes had occurred. In order to determine a detailed rupture model, Interferometric Synthetic Aperture Radar (InSAR) images and teleseismic data sets were objectively weighted by using a modified Akaika's Bayesian Information Criterion (ABIC) method to jointly invert for the rupture process of the earthquake. In modeling the rupture process, a constrained waveform length method, unlike the traditional subjective selected waveform length method, was used since the lengths of inverted waveforms were strictly constrained by the rupture velocity and rise time (the slip duration time). The optimal rupture velocity and rise time of the earthquake were estimated from grid search, which were determined to be 2.0 km/s and 20 s, respectively. The inverted model shows that the event is dominated by thrust movement and the released moment is 5.75 × 10 20 Nm (Mw 7.77). The slip distribution extends southward along the Ecuador coast line in an elongated stripe at a depth between 10 and 25 km. The slip model is composed of two asperities and slipped over 4 m. The source time function is approximate 80 s that separated into two segments corresponding to the two asperities. The small magnitude of the slip occurred in the updip section of the fault plane resulted in small tsunami waves that were verified by observations near the coast. We suggest a possible situation that the rupture zone of the 2016 earthquake is likely not overlapped with that of the 1942 earthquake. [ABSTRACT FROM AUTHOR]

Various observations are made to invert for the source model of the 2015 Gorkha earthquake. Previously published slip models involve different slip distributions and slip amplitudes. To obtain a robust model, we jointly invert for the rupture process of the Gorkha earthquake using three types of observations: Global Positioning System (GPS), Interferometric Synthetic Aperture Radar (InSAR), and teleseismic P wave data. Three constraints (i.e., spatial and temporal smoothness and minimum moment constraints) are applied to regulate the rupture process. The weight ratios between data sets and prior constraints are determined from a new developed generalized Akaike’s Bayesian Information Criterion (gABIC) weight determination method. This gABIC method can simultaneously and objectively weigh various kinds of observations and prior constraints, rather than being limited to the two types in the traditional ABIC method. The inverted slip model reveals the seismic moment of the earthquake is 9.40 × 10 20 N m released primarily in the first 60 s, equivalent to Mw 7.92. The rupture front propagates unilaterally along the strike direction and spreads in both the strike and dip directions. The slip distribution shows one large slip patch with two peaks along the strike direction with a maximum slip amplitude of approximately 7.6 m and identifies large slips (> 2 m) that occur in the updip section of the Main Himalayan Thrust (MHT) fault plane. Our results indicate that the released slip amplitude is larger than the accumulated slip amplitude since 1833, so the 2015 earthquake likely does not overlap with the 1833 earthquake. [ABSTRACT FROM AUTHOR]

Recently there have occurred the Manyi-Kangding earthquake sequence, including the 1997 Manyi, 2001 Kokoxili, 2008 Yutian, 2008 Wenchuan, 2010 Yushu, 2013 Lushan, 2014 Yutian and 2014 Kangding earthquakes, along the periphery of the Bayan Har block on the northern Tibetan Plateau. We employ the Coulomb failure model to probe the stress triggering effects on this sequence in terms of coseismic, postseismic and interseismic Coulomb stress changes. We examine the Coulomb stress changes from both the Manyi-Kangding sequence and other large earthquakes from 1411 to 2012 around the Bayan Har block and interseismic tectonic stressing. We use a stratified spherical postseismic relaxation model to compute postseismic Coulomb stress changes. We develop an explicit spherical least-squares collocation model to calculate interseismic Coulomb stress changes. Our results indicate that when merely considering triggering effects because of earthquakes from the Manyi-Kangding sequence, the compounded Coulomb stress changes of the coseismic and postseismic Coulomb stress changes are generally insignificant, except for the 2013 Lushan earthquake (0.14 bar). This general insignificance of Coulomb stress changes imparted by the Manyi-Kangding sequence agrees with previous studies, although interseismic Coulomb stress changes always load each hypocenter. On the other hand, when surrounding prior M ≥ 6.0 earthquakes are considered, we found that the compounded Coulomb stress changes become significant, ranging from 0.14 to 10.4 bars according to the constant apparent friction Coulomb failure model with an intermediate coefficient of 0.4. Therefore, all eight earthquakes are well explained by Coulomb stress changes when thoroughly considering large earthquakes around the Bayan Har block. Our findings indicate the importance of considering a broader group of neighboring large earthquakes for Coulomb stress analysis. [ABSTRACT FROM AUTHOR]

Postseismic deformation is one of the few geophysical phenomena that can be used to obtain the rheological properties of the lithosphere and provide key information for understanding stress variations that are induced by the mainshock or aftershock. On November 12, 2017, the Mw 7.3 Darbandikhan earthquake struck the border between Iran and Iraq, causing heavy casualties and property losses. Here, we first use the multidimensional small baseline subset technique to obtain the 2D postseismic deformation field from Interferometric Synthetic Aperture Radar data within ∼228 days after the event. The 2D postseismic deformation field shows that the main deformation region exhibits westwards horizontal movement with a maximum displacement of 7.5 cm, while the maximum uplift and subsidence reach 8.2 cm and 4.7 cm in the southwestern and northeastern areas of the main deformation region, respectively. Then, we choose preferred faults of co- and post-seismic slip distributions by considering the distribution of co- and post-seismic slip, aftershock precision location results, data misfits, and the Coulomb failure stress change from previous studies and use a joint model to simultaneously estimate the afterslip distribution and viscosity of the lower crust in the Zagros Mountains. As a result, the joint inversion performed on the flat-ramp-flat fault (preferred fault) suggests that the lower bound of the preferred viscosity of the lower crust beneath the Zagros Mountains is 3 × 1018 Pa s, the afterslip is distributed both up- and down-dip of the coseismic slip region, and the maximum slip of 0.61 m is located up-dip of the coseismic rupture. The cumulative seismic moment caused by the afterslip is 2.97 × 1019 N m, which is equivalent to a Mw 6.94 earthquake. Moreover, the stability and reliability of faults and the joint model are verified through Monte Carlo inversions. • we use the multi-dimensional small baseline subset technique to obtain the 2 D post-seismic deformation field from InSAR data within ∼228 days after the event. • the listric fault and flat-ramp-flat fault are regard as the preferred faults of co- and post-seismic slip distributions. • we use a joint model to simultaneously estimate the afterslip distribution and the viscosity of the lower crust in the Zagros Mountains. [ABSTRACT FROM AUTHOR]

Abstract: We invert the stressing rates of major strike-slip faults in the Tibetan Plateau using GPS measurements by the method of Least-Squares Collocation. From the comparison results of the influence of different distance intervals and covariance functions on the fit to GPS velocity field and the statistics of variance and covariance, we choose 40km as the distance interval and exponential function as the covariance function to calculate the stressing rates. The results show that the root-mean-square error of GPS observations is only 0.061cm. The stressing rates of the faults in the eastern Tibetan Plateau are generally higher than those in the west. The faults, whose maximum stressing rates are larger than 2.0kPa/yr, account for about 41.4% of selected faults. Specifically, the stressing rate of the northwest segment of the XSHF is the highest with a value of 7.05kPa/yr. Our stressing rates of the KLF and XSHF are consistent with published values or deduced results from published stress drops and earthquake recurrence intervals. The comparison results of stressing rates with fault slip rates show that the ratios of the stressing rates to the slip rates range broadly from 0.4 to 7.5bar/m, which may be due to different kinds of data and methods used to calculate the slip rates besides varying petrophysical properties in the Tibetan Plateau. However this variation of the same fault is less distinct than that in different faults. The GYFF, HYF, JLF, LCRF and RRF with low slip rates and high stressing rates may be located in brittle shear zones. Inversely, the ATF, KLF, KRKRF and KRKXF may be located in ductile zones. Additionally, the statistical results between the stressing rates and the seismicity rates show that the seismicity roughly grows with the tectonic stressing rates. And we deduce that the KRKXF and MCRCF with high seismicity rates and low stressing rates are the strike-slip faults mostly prone to rupture in the Tibetan Plateau. [Copyright &y& Elsevier]

Abstract: On October 6, 2008, an Mw 6.3 earthquake occurred in Dangxiong county, southern Tibetan Plateau. In this study, Synthetic Aperture Radar (SAR) images from Envisat ASAR C-band descending Track 176 and ALOS PALSAR L-band ascending Track 500 are processed to generate the coseismic deformation caused by the earthquake. To estimate the source model, a downhill simplex non-linear inversion method is used to determine the fault rupture geometry, and an automatic fault discretization technique is employed to divide the fault plane to construct the optimal slip model, in which the uncertainties of the fault parameters are assessed by a Monte Carlo method. The inversion results show that the earthquake strikes almost south–north and has a normal faulting focal mechanism with rake angle and slip of −111.7° and 1.33m, respectively. Peak slip of 2.15m is located at a depth of 7.5km. The estimated geodetic moment is 4.06×1018 N m (Mw 6.37), 71.2% of which is released in the depth range 4.5–11km. The slip model suggests that coseismic slip also takes place at some fault patches near the earth’s surface and postseismic afterslip occurs below the coseismic rupture area after the earthquake. [Copyright &y& Elsevier]

Abstract: InSAR time series techniques can provide high-spatial resolution deformation fields across an active fault belt, even for zones with heavy vegetation coverage. An interseismic deformation map across the Garze–Yushu fault belt in the Tibetan Plateau, ∼300km by ∼100km, is derived from C-band Envisat/ASAR imagery collected between 2003 and 2010. Unlike previous research, we obtain a lookup figure which relates the slip rate with the fault locking depth, the dip angle and the rake angle. The estimated slip rate changes significantly with the locking depth and the rake angle, but relatively little with the dip angle. When considering the focal mechanism solutions of historical earthquake along the Garze–Yushu fault, the interseismic slip rate of the Garze–Yushu fault is close to a value of 6.4mm/yr, which is between the highest (18.2mm/yr) and the lowest (3.1mm/yr) slip rate from GPS estimations, but slightly less than the minimum value (∼ 7mm/yr) from the geological estimations. The earthquake recurrence interval on the Yushu part of Garze–Yushu fault equals 272yr, and the April 14, 2010 Mw 6.9 earthquake has not completely released the accumulated strain energy between 1738 and 2010. [Copyright &y& Elsevier]

Abstract: We use interferometric synthetic aperture radar (InSAR) observations to investigate the coseismic deformation and slip distribution of the 1997 7.5 Manyi earthquake, a left-lateral strike-slip earthquake occurred on the west portion of the Kunlun fault in the northern Tibet, China. The fault trace is constrained by the combination of interferometric coherence image and azimuth offset image. The total length of the identified fault is about 170km. We estimate the source parameters using a seven-segment fault model in a homogeneous elastic half-space. We first use a uniform slip model to estimate the slip, width, dip and rake for each segment, resulting in a maximum slip of 5.5m with a depth of 11km on the fourth segment. The average dip of the uniform slip model is about 93° northward and the average rake is about −2°. We then use a distributed slip model to estimate the pure strike-slip and oblique slip distribution, respectively. In the distributed slip model, the fault plane is discretized into 225 patches, each of them 4km×4km. We fix the optimal geometric parameters and solve for the slip distribution using a bounded variable least-squares (BVLS) method. We find a geodetic moment of 1.91×1020 Nm (7.5), of which almost 68% released in the uppermost 8km and 82% in the uppermost 12km. For all the models used in this study, the synthetic profiles along strike show asymmetric displacements on the opposite sides of the fault, which are in agreement with the observations. This suggests that a linear elastic model with variable and non-vertical dips is also reasonable for the mechanism of the Manyi earthquake. [Copyright &y& Elsevier]

On 7 November 2019, an Mw 5.9 earthquake with a left-lateral strike-slip mechanism struck the Bozgush mountain in NW Iran, marking the largest event in the mountain area in the past 44 years. Because no surface rupture associated with the earthquake has been reported, the causative fault of the earthquake is unknown. This event provides an opportunity to gain insight into the active tectonics of the region. Here, we acquire the coseismic deformation associated with this earthquake through Sentinel-1A interferometric synthetic aperture radar (InSAR) data and further invert the fault geometry and the detailed coseismic slip of this event based on the planar fault model. By a joint analysis of the inversion results, aftershocks sequence and local tectonics, we propose that the buried branch fault splaying from the Shalgun-Yelimsi fault (SYF) at depth may be responsible for this earthquake. Both the uniform and distributed slip models infer a smaller fault rupture size than predicted by classical fault scaling relation. We suggest that the subsurface fault geometry of the SYF may stop the rupture propagation further down to southeast at depth, thus resulting in high slip and stress drop at such a small fault plane. Considering the proximity of the epicenter to the SYF, we also invert for the distributed slip model on an anti-listric fault with the purpose to explore the possible complexity of rupture fault. However, due to the lack of obvious improvement to fit the observed data and the limited slip in the deep fault segment, the planar fault model is still regarded as the optimal one. According to the calculated coseismic Coulomb stress changes, we find that 55 % of aftershocks are triggered by the statics stress and that the northern segment of SYF and the eastern segment of SBF have a potential rupture risk. The occurrence of this earthquake, together with the prominent offset feature and slip style of surrounding active fault, indicates an active conjugate fault system, which may accommodate the small-scale northeastward lateral extrusion. [ABSTRACT FROM AUTHOR]

Rapid disaster response will provide significant information to relevant responding agencies. On 20 March 2019, an Mw 5.7 earthquake struck the Acipayam basin in southwestern Turkey, which is the largest event to occur in the basin. Here, we use Sentinel-1A interferometric synthetic aperture radar (InSAR) data to investigate the cosesimic deformation related to the Acipayam earthquake. The ascending and descending interforegrams suggest the normal faulting during this earthquake, with the maximum line of sight (LOS) displacements of 4.6 cm and 4.8 cm, respectively. The fault geometric parameters and a detailed coseismic distributed slip model of this event are retrieved by using geodetic data for the first time. Though the coseismic interferograms don't show enough polarity changes to ascertain the dip orientation of the rupture fault, we regard the northeast-dipping fault as the causative fault by a joint analysis of the residuals plots, 2.5 dimensional (2.5D) deformation field, field investigation results, regional geomorphic feature and overall distribution of aftershock (4.0 < Mw < 4.9). The inversion results show that coseismic rupture was mainly dominated by normal faulting with minor sinistral strike-slip components. The rupture fault is a blind normal fault and the main slip is concentrated in the depth range of 3∼9.5 km with a maximum slip of approximately 0.33 m at a depth of ∼6 km. The InSAR-determined geodetic seismic moment is 3.96 × 1017 Nm corresponding to M w 5.7. Our model resolution test supports these interpretations for the Acipayam earthquake. Based on the coseismic Coulomb stress change, we find that this 2019 event increases the stress loading in the northwestern and southeastern segment of the rupture fault plane and possibly triggers the subsequent Mw 4.8 and Mw 4.9 earthquakes. The mechanism of the determined seismogenic fault may be helpful to evaluate seismic hazards and understand the evolution of the Acipayam basin. [ABSTRACT FROM AUTHOR]

The acquisition of a 3D displacement field can help to understand the crustal deformation pattern of seismogenic faults and deepen the understanding of the earthquake nucleation. The data for 3D displacement field extraction are usually from GPS/interferometric synthetic aperture radar (InSAR) observations, and the direct solution method is usually adopted. We proposed an iterative least squares for virtual observation (VOILS) based on the maximum a posteriori estimation criterion of Bayesian theorem to correct the errors caused by the GPS displacement interpolation process. Firstly, in the simulation examples, both uniform and non-uniform sampling schemes for GPS observation were used to extract 3D displacement. On the basis of the experimental results of the reverse fault, the normal fault with a strike-slip component, and the strike-slip fault with a reverse component, we found that the VOILS method is better than the direct solution method in both horizontal and vertical directions. When a uniform sampling scheme was adopted, the percentages of improvement for the reverse fault ranged from 3% to 9% and up to 70%, for the normal fault with a strike-slip component ranging from 4% to 8% and up to 68%, and for the strike-slip fault with a reverse component ranging from 1% to 8% and up to 22%. After this, the VOILS method was applied to extract the 3D displacement field of the 2008 Mw 7.9 Wenchuan earthquake. In the East–West (E) direction, the maximum displacement of the hanging wall was 1.69 m and 2.15 m in the footwall. As for the North–South (N) direction, the maximum displacement of the hanging wall was 0.82 m for the southwestern, 0.95 m for the northeastern, while that of the footwall was 0.77 m. In the vertical (U) direction, the maximum uplift was 1.19 m and 0.95 m for the subsidence, which was significantly different from the direct solution method. Finally, the derived vertical displacements were also compared with the ruptures from field investigations, indicating that the VOILS method can reduce the impact of the interpolated errors on parameter estimations to some extent. The simulation experiments and the case study of the 3D displacement field for the 2008 Wenchuan earthquake suggest that the VOILS method proposed in this study is feasible and effective, and the degree of improvement in the vertical direction is particularly significant. [ABSTRACT FROM AUTHOR]

The Mw 7.1 Anchorage earthquake on 30 November 2018 beneath the south‐central Alaska is a rare intermediate‐depth event larger than Mw 7 that occurred in a complex subduction region, where the young Yakutat oceanic terrane wedges in the continental‐oceanic plate collisional region between the Pacific oceanic plate and the North American plate. We use both ascending and descending Sentinel‐1 satellite Interferometric Synthetic Aperture Radar (InSAR) images to construct the coseismic displacement associated with this earthquake, which shows a nearly circular deformation pattern with a subsidence of ~4 cm in line of sight direction. Combining coseismic GPS data, we determine the focal mechanism of this event dominated by normal faulting with N‐S striking of 186° and westward dipping of 64° by using a uniform slip model. Then we find a preferred slip model with both geodetic data and teleseismic data, suggesting the main slips are concentrated on a depth of 55–75 km. The total released moment of our preferred slip model is 5.32 × 1019 N·m, equivalent to Mw 7.1. The rupture process includes two peaks terminating at about 18 s and indicates a unilateral rupture with its front propagating northwestward direction at an average speed of 2.5 km/s. In comparison with the detailed seismic image in this region, this event just occurred in the Yakutat terrane beneath a low velocity zone, suggesting it was caused by slab tear but not slab boundary breaking and determining the lower boundary of shallow thrust‐slip in the Alaska subduction zone. Key Points: An intermediate‐depth earthquake with ~4 cm coseismic displacement is revealed by InSAR measurementsThe determined rupture slips are concentrated on depth 55–70 km beneath a low velocity zone in the Yakutat terraneThe normal faulting was driven by downdip extensional stresses due to slab bending [ABSTRACT FROM AUTHOR]

In this study, Sentinel-1 and Advanced Land Observation Satellite-2 (ALOS-2) interferometric synthetic aperture radar (InSAR) and global positioning system (GPS) data were used to jointly determine the source parameters and fault slip distribution of the Mw 6.6 Hokkaido eastern Iburi, Japan, earthquake that occurred on 5 September 2018. The coseismic deformation map obtained from the ascending and descending Sentinel-1 and ALOS-2 InSAR data and GPS data is consistent with a thrust faulting event. A comparison between the InSAR-observed and GPS-projected line-of-sight (LOS) deformation suggests that descending Sentinel-1 track T046D, descending ALOS-2 track P018D, and ascending ALOS-2 track P112A and GPS data can be used to invert for the source parameters. The results of a nonlinear inversion show that the seismogenic fault is a blind NNW-trending (strike angle ~347.2°), east-dipping (dip angle ~79.6°) thrust fault. On the basis of the optimal fault geometry model, the fault slip distribution jointly inverted from the three datasets reveals that a significant slip area extends 30 km along the strike and 25 km in the downdip direction, and the peak slip magnitude can approach 0.53 m at a depth of 15.5 km. The estimated geodetic moment magnitude released by the distributed slip model is 6.16   × 10 18   N · m , equivalent to an event magnitude of Mw 6.50, which is slightly smaller than the estimates of focal mechanism solutions. According to the Coulomb stress change at the surrounding faults, more attention should be paid to potential earthquake disasters in this region in the near future. In consideration of the possibility of multi-fault rupture and complexity of regional geologic framework, the refined distributed slip and seismogenic mechanism of this deep reverse faulting should be investigated with multi-disciplinary (e.g., geodetic, seismic, and geological) data in further studies. [ABSTRACT FROM AUTHOR]

On November 18, 2017, the Mainling Mw 6.5 earthquake occurred on the northern Namche Barwa syntaxis and was the largest earthquake in the syntaxis and surrounding areas since the Zayu Mw 8.4 earthquake in 1950. Due to inconvenient access and the severe environment in the Namche Barwa syntaxis area, the motions and tectonic structures of most faults remain unclear. Sparsely distributed seismic observation stations make the seismogenic fault and focal mechanism of the Mainling earthquake controversial. We adopt interferometric synthetic aperture radar (InSAR) to invert the slip distribution of this event by defining the fault geometry with relocated aftershocks. Our preferred model suggests that the 2017 Mainling earthquake ruptured two blind faults beneath the Namche Barwa syntaxis. The ruptures were dominated by thrusts with slight right-lateral strike-slip components. The slips on the two faults are equivalent to moment magnitudes of Mw 6.12 and Mw 6.34, with maximum dislocation magnitudes of 0.36 m and 0.43 m, respectively. The model fits well with the InSAR observations and the distribution of aftershocks. The results from the Coulomb stress simulation indicate that the stress loading caused by strong historical events promoted the occurrence of the 2017 Mainling earthquake. Compared with the seismogenic faults of the Mainling earthquake, the larger thrust faults in the southern Namche Barwa syntaxis can generate larger earthquakes. Therefore, we assume that Mw > 6.5 earthquakes may occur beneath the Namche Barwa syntaxis and that the seismic risk has been further promoted by historical events. [ABSTRACT FROM AUTHOR]

The 28 September 2018 Mw 7.5 Palu earthquake occurred at a triple junction zone where the Philippine Sea, Australian, and Sunda plates are convergent. Here, we utilized Advanced Land Observing Satellite-2 (ALOS-2) interferometry synthetic aperture radar (InSAR) data together with broadband regional seismograms to investigate the source geometry and rupture kinematics of this earthquake. Results showed that the 2018 Palu earthquake ruptured a fault plane with a relatively steep dip angle of ~85°. The preferred rupture model demonstrated that the earthquake was a supershear event from early on, with an average rupture speed of 4.1 km/s, which is different from the common supershear events that typically show an initial subshear rupture. The rupture expanded rapidly (~4.1 km/s) from the hypocenter and propagated bilaterally towards the north and south along the strike direction during the first 8 s, and then to the south. Four visible asperities were ruptured during the slip pulse propagation, which resulted in four significant deformation lobes in the coseismic interferogram. The maximum slip of 6.5 m was observed to the south of the city of Palu, and the total seismic moment released within 40 s was 2.64 × 1020 N·m, which was equivalent to Mw 7.55. Our results shed some light on the transtensional tectonism in Sulawesi, given that the 2018 Palu earthquake was dominated by left-lateral strike slip (slip maxima is 6.2 m) and that some significant normal faulting components (slip maxima is ~3 m) were resolved as well. [ABSTRACT FROM AUTHOR]

The recent development of imaging geodesy, an advanced technique with a high spatial resolution and large-scale coverage, has enabled researchers to obtain multiple high-quality surface displacement estimates at low labor-cost, thereby improving the capability to monitor and manage geological disasters. The different sources (e.g., radar, optical and LiDAR sensors) and analysis approaches (e.g., differential interferometric synthetic aperture radar, DInSAR; multiple-aperture InSAR; pixel offset tracking; and iterative closest point, ICP) in imaging geodesy used to derive displacement estimates have unique benefits and drawbacks. However, the inherent differences among these data sources and methods in the construction of three-dimensional (3D) deformation maps, particularly in the near field, remain poorly understood and require further discussion. In this study, we acquired three pairs of ALOS-2 stripmap mode images, two pairs of Sentinel-1 TOPS mode images and pre- and post-event LiDAR data for the 2016 Kumamoto earthquake to explore the 3D near-field displacements using various imaging geodesy techniques with different types of image information, i.e., SAR phase data, SAR amplitude data and LiDAR point cloud data. Our results show that each image type is independently capable of producing a high-quality 3D deformation map for the 2016 Kumamoto earthquake with an on-fault accuracy of <43 cm determined from field work measurement, and an off-fault accuracy of <14 cm determined from GNSS observations. The major contributors to the uncertainty in the 3D deformation estimates from the SAR phase, SAR amplitude, and LiDAR data methods are the effective Doppler bandwidth, pixel resolution and topographic roughness, respectively. In the near-field deformation region, more secondary fault ruptures were revealed by SAR amplitude and LiDAR information than by the SAR phase information, thereby overcoming the sensitivity of the SAR phase signal to incoherence. Finally, an integrated complete 3D map was generated to constrain the coseismic rupture behavior of the Kumamoto earthquake sequence associated with the Futagawa and Hinagu faults. Our slip model suggests the main slip rupture a length of 32 km and terminated near the rim of the Aso caldera; additionally, the slip pattern delineated by three asperities that was dominated by right-lateral strike-slip with a minor normal slip component at a depth of 7 km. Furthermore, the main rupture triggered two secondary faults with right-lateral strike-slip and normal slip. Our source model yields a geodetic moment of 5.77 × 1019 N·m, which corresponds to Mw 7.11. • The bandwidth, pixel size or terrain roughness can affect the imaging geodesy. • SAR phase or amplitude, or LiDAR data can derive high-quality 3D displacement. • SAR amplitude and LiDAR data are very useful for on-fault rupture displacement. • Main and secondary faults revealed by our integrated complete 3D displacement. [ABSTRACT FROM AUTHOR]

Abstract Current afterslip models of the Mw 7.8 Gorkha earthquake contradict with the depth ranges of relocated aftershock distribution and inter-seismic locked-creeping transition zone. We use both GPS and interferometric synthetic aperture radar (InSAR) data to image the afterslip evolution in the first 189 post-seismic days, i.e., from 25 April to 1 November 2015. In the study region, 51 GPS stations are divided into three categories based on their observation time: (1) 25 stations with both pre- and post-seismic observations, (2) 16 stations with only post-seismic observations, and (3) 10 stations with only pre-seismic observations. The secular tectonic motion and seasonal variations are corrected carefully and directly using the fitted functions from the pre-seismic position time series. During the inversions, we adopt the widely accepted flat–ramp–flat geometrical model of the Main Frontal Thrust fault (MFT)–Main Himalayan Thrust fault (MHT). The preferred weight ratios between GPS and InSAR observations are elaborately determined through comprehensive analysis of model resolution and fitting residuals. In contrast to previous afterslip models, our preferred afterslip distributes on the crustal ramp of the MHT from depths of 11 to 29 km, which is verified by further inversions using only GPS data and checkerboard resolution tests. The seismic moment released by the afterslip in the first six months is 3.42 × 1019 N m, only approximately 4% of the mainshock moment. The rupture gap between the mainshock and the 12 May aftershock is filled up with post-seismic aseismic slip. Highlights • GPS observations in the study region are carefully sorted and corrected. • Afterslip occurred on the crustal ramp of the Main Himalayan Thrust from depths of 11 km to 29 km. • The rupture gap between the mainshock and the 12 May aftershock is filled up with afterslip. • The seismic moment released in first six months is about 4% of the mainshock moment. • Prominent afterslip occurred in the first two months accounts for 56% of the total moment. [ABSTRACT FROM AUTHOR]