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The MW7.3 Sarpol Zahab earthquake that occurred in the Zagros Fold-Thrust Belt (ZFTB) of Iran on November 12, 2017 is the largest earthquake instrumentally recorded in the region. This earthquake provides an opportunity to investigate the slip behaviour and frictional properties of the fault, which is significant for assessing future seismic potential. In this study, we use Sentinel-1 images to map the co- and post-seismic deformation to invert for the fault slip. The result indicates that most of the coseismic slip is buried in the depth range of 11–17 km, and the maximum slip is about 3.8 m at a depth of 15 km. The coseismic slip induces an increase of Coulomb stress in the unruptured area of the seismogenic fault plane, driving the afterslip. Based on the stress-driven afterslip, we obtain a frictional parameter of (a − b) = (0.001 − 0.002) for the updip afterslip zone and (a − b) = 0.0002 for the downdip afterslip zone in the framework of rate-and-state friction. The constitutive parameter (a − b) of the fault is very small, suggesting that the fault segments are close to velocity-neutral and may experience coseismic rupture.

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]

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.

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]

A homogeneous or stratified viscoelastic half-space has often been used as a simple earth model to calculate the deformation induced by an earthquake or a regional deglaciation. Recent publications have shown that, when taking into account the coupling between the earth's gravity and the dilatational motion, the response of the model exhibits singularities for wavenumbers below a critical value (kg). It is shown here that the boundary-value problems based on such earth models have no solution at all for this low-wavenumber region. In fact, previous authors tried unintentionally to solve an unsolvable system by analytical or numerical extrapolation from the valid wavenumber rangeto the invalid range. Therefore, non-physical singularities appear in their numerical results. In particular, the previous elastic-gravitational dislocation theory includes an incorrect treatment of these singularities, which may lead to significant errors in the deformation models. This paper analyses the mathematical and physical causes for the unsolvability and proposes a consistent way to solve the difficulty. In particular, numerical tests show that an elastic-gravitational deformation model would become even less reliable than the corresponding elastic model, if the coupling between gravity and deformation were considered in the incorrect way published previously. [ABSTRACT FROM AUTHOR]