Combined with the multi‐array back‐projection and finite‐fault joint inversion methods, we investigate the detailed spatiotemporal rupture complexity of the 2021 MW 7.4 Maduo earthquake using seismic and geodetic data. Our results reveal that this earthquake ruptured bilaterally 170 km long fault segments with a duration of 38 s. The obtained back‐projection results, specific aftershock signature of the supershear earthquake, and observations of far‐field Love Mach waves consistently validate that this earthquake is a supershear event. Furthermore, by analyzing global large strike‐slip earthquakes, we find that the moment‐scaled radiated energies of previously well confirmed supershear earthquakes with relatively simple fault geometries are similar to that of the 2021 MW 7.4 Maduo earthquake, which are significantly smaller than those of subshear strike‐slip events. This new finding provides additional supporting evidence to validate the supershear rupture during the 2021 MW 7.4 Maduo earthquake.

On 5 September 2022, an Mw 6.6 strike-slip earthquake occurred in Luding, Sichuan, China. It illuminates the seismic gap on the southern end of Xianshuihe fault zone, that is Moxi segment, and is the most damaging earthquake in Chinese Mainland since 2014. In this article, we use multiple seismological methods to analyze the basic characteristics of the Luding earthquake, including its source parameters, rupture process, aftershock distribution, and further discuss its implications on preseismic fault behavior and impact on short-term seismic hazard. Using near-field stations, we first revisit the source parameters of the mainshock and obtain a much shallower hypocentral depth (∼9.3 km) than previously reported. Next, we jointly inverse the teleseismic P-wave data and near-field strong-motion data to constrain the mainshock rupture process. The coseismic slip consists of two subevents that spans for ∼20 km and shows an overall unilateral rupture to the south-southeast direction. The earthquake has 90% of the seismic moment released in its first 10 s. Third, we relocate the first 34 days of aftershocks with both manual phase picks and cross correlation, and finally obtain 5269 well-located events. The aftershocks reveal a near-vertical Xianshuihe fault and two sets of unmapped faults off the major Xianshuihe fault: one set of strike-slip faults on the north-northwest of rupture and the other one on the west of mainshock that generates the most intense seismicity with prevalent normal faulting. By examining the aftershock evolution and Coulomb stress change, we find that postseismic processes evolve both on and off the major fault, and the western off-fault system has highly variable fault orientations. Finally, we calculate the Coulomb stress change by the Luding earthquake on surrounding faults. Results show that the north Anninghe fault is significantly loaded by the Luding earthquake (>0.1 MPa), which poses high seismic hazard in the short term.

On 21 May 2021, an Mw 6.1 earthquake, causing considerable seismic damage, occurred in Yangbi County, Yunnan Province of China. To better understand the surface deformation pattern, source characteristics, seismic effect on nearby faults, and strong ground motion, we processed the ascending and descending SAR images using the interferometric synthetic aperture radar (InSAR) technique to capture the radar line-of-sight (LOS) directional and 2.5-dimensional deformation. The source model was inverted from the LOS deformation observations. We further analyzed the Coulomb failure stress (CFS) transfer and peak ground acceleration (PGA) simulation based on the preferred source model. The results suggest that the 2021 Yangbi earthquake was dextral faulting with the maximum slip of 0.9 m on an unknown blind shallow fault, and the total geodetic moment was 1.4 × 1018 Nm (Mw 6.06). Comprehensive analysis of the CFS transfer and geological tectonics suggests that the Dian–Xibei pull-apart basin is still suffering high seismic hazards. The PGA result demonstrates that the seismic intensity of this event reached up to VIII. The entire process from InSAR deformation to source modeling and strong ground motion simulation suggests that the InSAR technique will play an important role in the assessment of earthquake disasters in the case of the shortening of the SAR imaging interval.

No abstract

The 17 June 2019 Ms 6.0 Changning earthquake occurred on the southern margin of the Sichuan basin in China, which breaks the historical record for the largest earthquake in the Sichuan basin. Based on the abundant local seismic, strong motion, and Interferometric Synthetic Aperture Radar line of sight displacement data, we investigate the detailed source characteristics of this earthquake sequence. We determine focal mechanisms of 68 ML≥2.0 aftershocks with P wave first-motion polarities and S/P amplitude ratios. The triangle diagram of focal mechanisms shows that 82% of the aftershocks have thrust faulting mechanisms. The spatial distribution of aftershocks together with the determined focal mechanisms indicates that this earthquake sequence was mainly controlled by the southeast–northwest-extended faults. In addition, the revealed diversity of aftershock focal mechanisms implies that some small subsidiary faults with different geometries and motion features have likely been ruptured. The kinematic finite-fault joint inversion results reveal a complex rupture process of the mainshock on two fault segments with different geometries. The rupture initiated on the southeastern fault segment with a gentle dip angle and then jumped to the vertical northwestern fault segment. The main rupture length and duration are approximately 11 km and 8 s, respectively. The released total scalar seismic moment during the rupture process is 4.6×1017  N·m, corresponding to a moment magnitude of Mw 5.7. Our results suggest that the nucleation and the rupture initiation and propagation of the 2019 Ms 6.0 Changning earthquake sequence were likely controlled by the intrinsic structure and stress heterogeneities of the involved seismogenic faults, as well as the variation in pore-fluid pressure caused by the long-term water injection in the Changning salt mining area and adjacent areas.