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The thickness estimation of landslides is crucial for better landslide evaluation. Traditional non-contact mass conservation methods using 3D deformation may be unsuitable due to observation limitations. This study proposes a more feasible approach based on 2D deformation from two-track Interferometric Synthetic Aperture Radar (InSAR) observations, applied to the Xiongba landslide. The comparison with geological and drilling measurements confirms the reliability of this method. The mapped InSAR LOS deformation rate fields reveal two regions: a significantly deformed frontal zone and a relatively stable zone. Analysis suggests that surface uplift at the Xiongba-H2 landslide's front edge results from rock–soil mass pushing in high-deformation areas. The estimated thickness ranges from 10 to 100 m, with an active volume of 6.17 × 107 m3. A thicker region is identified at the front edge along the Jinsha River, posing the potential for further failure. This low-cost, easily implemented approach enhances InSAR's applicability for landslide analysis and hazard assessment. [ABSTRACT FROM AUTHOR]

The Main Recent Fault (MRF) is an important boundary fault that accommodates the oblique convergence motion between the Arabian and Eurasian plates. Several large earthquakes including the 1909 Mb 7.4, 1958-1963 three events with magnitude larger than Mw 6.0, and the 2006 Mw 6.1 earthquake had partly ruptured the central and southeast segments of MRF. However, there is no large earthquake occurred in the northwest segment in the past hundred years. In this study, the interseismic surface deformation was firstly mapped from the Synthetic Aperture Radar (SAR) images observed by the Sentinel-1 satellite. Then, the ununiformed fault slip rate, coupling ratio and locking depth are estimated based on the measured interseismic surface deformation. The results show that the interseismic fault slip rate slightly varies from ~3.7 mm/yr to ~6.1 mm/yr along the MRF. Furthermore, it is also found a gradual increasing extensional component with magnitude of 2-7 mm/yr from Morvarid to Sahneh segments of MRF. In addition, total 9 sub-segments could be divided based on the fault coupling distribution and historical earthquakes in the interest zone. A seismogenic zone is identified from the historical earthquakes, which has a good space consistency with the transition between the significant shallow locking and deep free slip zones. According to the potential seismic magnitude and estimated recurrence interval, it is found that several segments are approaching the end of their interseismic recurrence interval. Meanwhile, one segment (SF-8) may be in the early stage of a new recurrence period due to the recent several large earthquakes and a long recurrence interval. [ABSTRACT FROM AUTHOR]

A doublet earthquake event including two main shocks with a magnitude larger than Mw 6.0 occurred on 1 July 2022 in the Zagros fold‐and‐thrust belt, southeast Iran. The coseismic InSAR deformation field shows that this event caused significant surface uplift due to fault‐related folding in the seismic zone. The estimated preferred faulting model suggests that a higher dip angle fault (maximum slip of ∼1.1 m), and an overlying gentle dipping fault (maximum slip of ∼1.2 m) within the Bandar‐e‐Lengeh Anticline, are responsible for the first and second main shocks, respectively. The calculated Coulomb failure stress change suggests that the first main shock and its Mw 5.7 aftershock have a significantly positive triggering effect in the second main shock. The accumulated interseismic strain should have been partly released by the two main shocks. Finally, the salt diapir activity may affect the generation of the earthquake in the seismic zone. Plain Language Summary: The doublet earthquake frequently occurred in the southeast part of the Zagros fold‐and‐thrust belt in the past years. In this study, we first adopted the Synthetic Aperture Radar images captured by Sentinel‐1 satellite to map the coseismic surface deformation of the 2022 Hormozgan doublet earthquake. The uplift of fault‐related folding controls the coseismic surface motion of these events from blind thrusting. Moreover, the two main shocks are caused by the rupture of two faults within the Bandar‐e‐Lengeh Anticline. Furthermore, the first main shock increased the stress in the source area of the second main shock, and positive triggered the rupture of the seismogenic fault of the second main shock. The interseismic surface deformation suggests that the 2022 Hormozgan doublet earthquake may have released the accumulated interseismic strain for the past ∼104 years. In addition, salt diapir activity in the southeast part of the seismic zone may contribute to the 2022 Hormozgan doublet earthquake. Key Points: A doublet earthquake occurred in the southeastern of Zagros fold‐and‐thrust belt with a significant salt layers activityA combination of steep and shallow blind faults is responsible for the 2022 Hormozgan doublet earthquakeThe interseismic strain accumulation and salt diapir activity in the southeast of the seismic zone may cause this doublet earthquake [ABSTRACT FROM AUTHOR]

We use interferometric synthetic aperture radar observations to investigate the fault geometry and afterslip evolution within 3 years after a mainshock. The postseismic observations favor a ramp‐flat structure in which the flat angle should be lower than 10°. The postseismic deformation is dominated by afterslip, while the viscoelastic response is negligible. A multisegment, stress‐driven afterslip model (hereafter called the SA‐2 model) with depth‐varying frictional properties better explains the spatiotemporal evolution of the postseismic deformation than a two‐segment, stress‐driven afterslip model (hereafter called the SA‐1 model). Although the SA‐2 model does not improve the misfit significantly, this multisegment fault with depth‐varying friction is more physically plausible given the depth‐varying mechanical stratigraphy in the region. Compared to the kinematic afterslip model, the mechanical afterslip models with friction variation tend to underestimate early postseismic deformation to the west, which may indicate more complex fault friction than we expected. Both the kinematic and stress‐driven models can resolve downdip afterslip, although it could be affected by data noise and model resolution. The transition depth of the sedimentary cover basement interface inferred by afterslip models is ∼12 km in the seismogenic zone, which coincides with the regional stratigraphic profile. Because the coseismic rupture propagated along a basement‐involved fault while the postseismic slip may activate the frontal structures and/or shallower detachments in the sedimentary cover, the 2017 Sarpol‐e Zahab earthquake may have acted as a typical event that contributed to both thick‐ and thin‐skinned shortening of the Zagros in both seismic and aseismic ways. Plain Language Summary: The 2017 Mw 7.3 Sarpol‐e Zahab earthquake is the largest instrumentally recorded event to have ruptured in the Zagros fold thrust belt. Although much work has been conducted for a better understanding of the relationship between crustal shortening and seismic and aseismic slip of the earthquakes in the Zagros, active debate remains. Here, we use interferometric synthetic aperture radar observations to study the fault geometry and afterslip evolution within 3 years after the 2017 Mw 7.3 Sarpol‐e Zahab earthquake. For postseismic deformation sources, afterslip and viscoelastic relaxation are considered to be possible causes of postseismic deformation. Our results show that the kinematic afterslip model can spatiotemporally explain the postseismic deformation. However, the mechanical afterslip models tend to underestimate the earlier western part of the postseismic deformation, which may indicate a more complex spatial heterogeneity of the frictional property of the fault plane. We find that there is deep afterslip downdip of coseismic slip from both the kinematic and stress‐driven afterslip models, although it could be affected by data noise and model resolution. We additionally find that the viscoelastic response is negligible. Postseismic slip on more complex geological structures may also be reactivated and triggered, combined with geodetic inversions, geological cross‐section data and local structures in the Zagros. Key Points: The Spatiotemporal evolution of postseismic observations favors a ramp‐flat structure in which the flat angle should be lower than 10°Depth‐varying friction is required to better simulate the rate‐strengthening afterslip evolutionDowndip afterslip can be resolved by afterslip models, although it relies on data accuracy and model resolution [ABSTRACT FROM AUTHOR]

Multi-source datasets, including the UAV-Lidar/Photogrammetry, InSAR, and field investigation data, have been used for revealing the complex surface displacement pattern and focal mechanism of the 2021 Maduo Mw 7.3 earthquake. First, a co-seismic surface deformation field was extracted from the Synthetic Aperture Radar (SAR) images captured by ALOS-2 and Sentinel-1 satellites. Second, the SAR pixel offset tracking results were adopted to detect the initial location of the seismogenic fault. Then, the Lidar digital elevation model with high spatial resolution and field investigation were employed to refine and verify the location of the seismogenic fault. It was found that bifurcated strike-slip rupture should account for the 2021 Maduo earthquake. As indicated by the estimated faulting model based on the InSAR data, the maximal fault slip was ~6.2 m, occurring in the southeast of the main seismogenic fault, and five remarkable slip concentrations controlled the surface displacement of the 2021 Maduo earthquake. Furthermore, the co- and post-seismic InSAR deformation, dilatation, shear strain, Coulomb failure stress, and aftershock sequence suggest that the co-seismic rupture of the two main seismogenic faults have triggered the aseismic slip along the Changmahe fault. Lastly, according to the Coulomb failure stress change due to the historical earthquakes and the 2021 Maduo earthquake, the 1937 M 7.8 earthquake predominantly controlled the Coulomb failure stress change along the Kunlun fault, and the Xidatan-Alake Lake and Maqin segments had a higher risk of future earthquake than the other segments. [ABSTRACT FROM AUTHOR]

An earthquake with a magnitude of M s 6.0 and shallow focal depth of ∼4 km struck the Changning county, Sichuan province, China on 2019 June 17. The hypocentre is located in the fold-and-thrust belt with plentiful shale gas and salt mine resources. One hypothesis is that the shallow fault could be affected by the artificial pressure water injection including the disposal of wastewater, fracking shale gas extraction and salt mining in Changning area. In this study, SAR (Synthetic Aperture Radar) images, historical earthquakes, aftershocks and seismic reflection data were collected to jointly investigate the characteristics of the 2019 Changning earthquake. The source model inferred from the InSAR coseismic deformation observation reveals that the 2019 Changning earthquake is attributed to a blind fault dipping to southwest with dominant thrust and sinistral strike slip. Moreover, a small shallow fault developing within the Changning anticline was triggered by the main shock, which contributed to the surface displacements as observed in the north of the epicentre. The estimated maximum slip of 0.49 m is located at the depth of ∼1.9 km, ∼9 km northwest of the epicentre. The Coulomb failure stress change caused by the previous two large earthquakes, which occurred in the hydraulic fracturing area, suggesting that they have little effect on the initial rupture of the 2019 Changning earthquake. Despite this, they have a positive triggering effect on the fault rupture in the northwest of the seismogenic fault. In addition, the analysis on the relation between the positive Coulomb failure stress change and the aftershocks suggests that the aftershocks may have different motion patterns from the main shock. The analysis also shows the earthquakes occurrence in the seismogenic zone may be affected by the high pore pressure due to the long-term injection of salt mining for more than three decades. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) interferometry (InSAR) is a geodetic tool widely applied in the studies of earth-surface deformation. This technique has the benefits of high spatial resolution and centimetre-scale accuracy. Differential SAR interferometry (DInSAR) is used to measure ground deformation with repeat-pass SAR images. This study applied DInSAR and persistent scatterers InSAR (PSInSAR) for detecting land subsidence in the Pingtung Plain, southern Taiwan, between 1995 and 2000. In recent years, serious land subsidence occurred along coastal regions of Taiwan as a consequence of over-pumping of underground water. Results of this study revealed that the critical subsidence region is located on the coast near the estuary of Linpien River. It is also found that subsidence was significantly higher during the dry season than the wet season. The maximum annual subsidence rate of the dry season is up to −11.51 cm/year in critical subsidence region and the vertical land movement rate is much slower during the wet season. The average subsidence rates in wet and dry seasons are −0.31 and −3.37 cm/year, respectively. As a result, the subsidence rate in dry seasons is about 3 cm larger than in wet seasons. [ABSTRACT FROM AUTHOR]

We investigate the slip distribution of the 2008 May 12 Wenchuan M 7.9 earthquake using GPS data and InSAR measurements under a linear inversion scheme, with emphasis on the effect of three factors, including constraint on rake, different discretizations, and layered elastic model. Within our inversion parameterization context, we find the most influential factor would be constraint on rake. Without constraint on rake, the slip model seems physically wrong under the depth of 15 km, due to the limited depth resolution of the geodetic data used, especially the one orbit of InSAR measurements. Thus it is necessary to add a priori to the slip rake to obtain a reasonable fault source model. Different discretizations of the subfault patches have a notable impact on the slip distribution. Also, the layered elastic model predicts more slip at depth than does the half-space model, by about 15-20 per cent. The characteristics of slip distribution established through our inversions include some points as follows: (1) the most reliable results would be expected at depth range of 0-15 km; (2) three peak-slip asperities are inverted, at Yingxiu county (near epicentre), Yuejiashan county, and Beichuan county, respectively; (3) the inverted rake along the Yingxiu-Beichuan fault changes from dominantly thrusting motion at the southwest segments to dominant right-lateral or even pure right-lateral strike slip at the northeast segments, and (4) only thrust slip is occurred on the Guanxian-Jiangyou fault. [ABSTRACT FROM AUTHOR]

Abstract: The D-InSAR technique is applied to detect the active fault-related folding structure of the Tainan tableland near the deformation front in SW Taiwan by using ERS SAR images during 1996–2000. The Tainan tableland is located in-between a blind fault in the west and the Houchiali fault in the east, thus the Tainan tableland is interpreted as a pop-up structure in a fold-thrust belt at active tectonic margin. Interferometric processing of six SAR images reveals the average slant range deformation (SRD) as ~12.5 mm/yr. The uplift rate is higher in eastern Tainan tableland than that in western Tainan tableland, and it increases from west edge of Tainan tableland and decreases across the Houchiali fault. The campaign-mode GPS data set from 1999 to 2003 indicate an average horizontal movement of 12±4 mm/yr in the direction of N44°W for the Tainan tableland with respect to western coastline. Furthermore 5 precise leveling surveys across Tainan tableland over a period of 2 years show an uplift rate of ~14 mm/yr for the benchmarks on the tableland. Based on the 2-D analytical solution with the constraint of he inferred fault geometry, the slip rate along the inferred Tainan fault is ~16 mm/yr, ~10 mm/yr along the Houchiali fault, and ~25 mm/yr along the inferred Chungchou fault. Consequently we propose that active deformation of the Tainan tableland is likely resulted from the freely slipping of the Tainan fault and the Houchiali fault. The locking depth should be located on the deeper part of décollement, eastern of the Chungchou fault. In addition, the combination of D-InSAR, GPS data and the precise leveling data reveals that the short-term deformation rate is larger than long-term deformation rate, which implies that a destructive seismic event could occur in the eastern Tainan area. [Copyright &y& Elsevier]

The ascending and descending InSAR deformations derived from ALOS-2 and Sentinel-1 satellite SAR images and GPS displacements are used to estimate the fault model of the 2018 Mw 6.4 Hualien earthquake. The sinistral strike-slip fault dipping to the west with a high dip angle of 89.4° and a rake angle of 201.7° is considered as the seismogenic fault of this event. This seismogenic fault also triggered the ruptures of the Milun fault, which dips to the east with a dip angle of ~72°, and an unknown west-dipping fault with a dip angle of 85.2°. Two predicted faulting models indicate that the InSAR deformation fields include more postseismic slip than those of the GPS data. The north segment of the Milun fault and west-dipping fault have been triggered by the rupture of the seismogenic fault, but the postseismic slip occurred only in the south segment of the Milun fault. The InSAR-derived co-seismic and postseismic faulting model suggests that the significant slip concentrates at depths of 2.4–15.0 km of the main fault, 0.0–14.0 km of the Milun fault. Only minor slip is detected on the west-dipping fault. The maximum fault slip of ca. 2.1 m is located at the depth of ca. 2.4 km under the Meilun Tableland. The Coulomb failure stress (CFS) change calculated by the co-seismic and postseismic faulting model shows that there is a significant CFS increase in the east of the south segment of the Milun fault, but few of the aftershocks occur in this area, which indicates a high risk of future seismic hazard. [ABSTRACT FROM AUTHOR]

Slow-moving landslides can be found worldwide, exhibiting gradual movement over years to decades, with velocities ranging from millimeters to meters per year. However, slow-moving landslides can undergo transformation into rapid and catastrophic events, leading to severe damage to human society. Given the presence of >2500 pre-existing slow-moving landslides identified and cataloged using LiDAR bare ground data in Taiwan, it is crucial to efficiently assess their activity prior to the typhoon and heavy rainfall seasons. Therefore, a key research objective is to enhance the ability to detect landslide velocities and movements over large areas spanning tens of thousands of square kilometers. This study aims to establish a workflow that employs the multitemporal interferometric synthetic aperture radar (MTInSAR) technique for the detection and monitoring of multiple slow-moving landslides across wide regions. Specifically, we propose an optimized analysis package called "multi-snap2stamps," based on the existing snap2stamps method, to generate interferograms for multiple regions simultaneously. Focusing on the analysis of nine pre-existing slow-moving landslides, with velocities <1.6 m/year (classified as very slow or extremely slow landslides according to established criteria), distributed across Taiwan with diverse terrain and geological conditions, this study investigates the characteristics of these deep-seated landslides using the proposed MTInSAR analysis workflow in both spatial and temporal domains. The results reveal that two slow-moving landslide sites exhibit significant seasonal signals in the time series, while seven sites do not display such signals. Additionally, the MTInSAR time series effectively captures accelerated movement in the Shiding-T001 landslide, which corresponds well with in situ inclinometer monitoring data. This study demonstrates the effective analysis of velocity distribution and movement characteristics of slow-moving landslides using the proposed MTInSAR workflow. Furthermore, it highlights the potential of this workflow for improving landslide motion detection over vast areas of interest in the future. • Simultaneous generation of SAR interferograms from multiple regions of landslides. • Optimizing an MTInSAR workflow for analysis of multiple slow-moving landslides. • Detecting accelerated movements of slow-moving landslides by time series analysis. • Implication of seasonal fluctuation signals from the MTInSAR time series. [ABSTRACT FROM AUTHOR]

We present precise deformation velocity maps for the two year period from September 2011 to July 2013 of the northern Taiwan area, Taipei, by using persistent scatterer interferometry (PSI) technique for processing 18 high resolution X-band synthetic aperture radar (SAR) images archived from COSMO-SkyMed (CSK) constellation. According to the result, the highest subsidence rates are found in Luzou and Wuku area in which the rate is about 15 mm/yr and 10 mm/yr respectively in the whole dataset. However, dramatic change from serve subsidence to uplift in surface deformation was revealed in the Taipei Basin in two different time spans: 2011/09–2012/09 and 2012/09–2013/07. This result shows good agreement with robust continuous GPS measurement and precise leveling survey data across the central Taipei Basin. Moreover, it also represents high correlation with groundwater table. From 8 well data in the Taipei basin, the storativity is roughly constant across most of the aquifer with values between 0.5 × 10 − 4 and 1.6 × 10 − 3 in Jingmei Formation and 0.8 × 10 − 4 and 1.4 × 10 − 3 in Wuku Formation. This high correlation indicated that one meter groundwater level change could induce about 9 and 16 mm surface deformation change in Luzou and Wuku area respectively, which is about eight times faster the long-term tectonic deformation rate in this area. Thus, to access the activity of the Shanchiao Fault, it is important to discriminate tectonic movement from anthropogenic or seasonal effect in the Taipei Basin to better understand the geohazards and mitigation in the Taipei metropolitan area. [ABSTRACT FROM AUTHOR]

Geodetically measured surface displacements are produced by a combination of underlying deformation processes acting at different spatial and temporal scales. A complete history of surface measurements in an area can help discriminate contributions from tectonic, hydrologic, and anthropogenic processes. In this study, we use Synthetic Aperture Radar (SAR) images of the active mountain front and adjacent coastal plain of southwestern Taiwan to generate time series of surface deformation from 1995 to 2001 and from 2005 to 2008 based on the InSAR small baseline method. The InSAR measurements agree well with LOS motions estimated from continuous GPS measurements of 3D displacements between 2006 and 2008. A significant range increase in line of sight (LOS) is dominated by land subsidence in the coastal area of western and southwestern Taiwan. Subsidence rates vary with annual periods and are highly correlated with seasonal precipitation, which are likely associated with groundwater recharge and withdrawal. The long-term deformation is dominated by long-term tectonic loading in SW Taiwan during the interseismic period of the earthquake cycle, including elastic strain along or continuous creep on the active faults. Our results show the ability of InSAR to reveal spatiotemporal crustal deformation in western Taiwan with high spatial resolution and accuracy, which is potentially important for evaluating seismic hazards. [ABSTRACT FROM AUTHOR]