The 5 September 2022 Mw 6.7 Luding earthquake occurred on the Moxi segment of the highly active Xianshuihe fault in eastern Tibet. Here, we constrain the coseismic slip by jointly inverting the coseismic displacements measured by Global Positioning System, seismometer and Interferometric Synthetic Aperture Radar. Along the Moxi fault, concentrated left‐lateral strike slip extends ∼30 km along the strike above 10 km depth, producing 0.7–1.0 m shallow slip. Clustered aftershocks and slip inversions suggest that the secondary conjugate Mozigou fault may also involve the rupture. Southward rupture propagation is likely arrested by the barrier‐like fault segments of the Xianshuihe fault, characterized by high interseismic coupling (>0.6) and reduced shear stress rate (<1 kPa/yr) due to interactions with surrounding large locked asperities. The distribution of aftershocks is highly correlated with the positive coseismic Coulomb failure stress changes , which bring the adjacent asperities on the Anninghe and Daliangshan faults ∼0.2 MPa closer to failure.
Peak ground displacement (PGD) and peak ground velocity (PGV) are critical parameters during earthquake early warning, as they can provide rapid magnitude estimation before rupture end. In this study, we used the high-rate Global Navigation Satellite System (GNSS) data from 55 continuous stations to estimate the magnitude of the 2021 Maduo earthquake in western China. We used the relative positioning method and variometric approach to acquire real-time GNSS displacement and velocity waveforms, respectively. The results showed the amplitude of displacement and velocity waveforms gradually decreased with increasing hypocentral distance. Our results showed that the fluctuation of PGD magnitudes over time is smaller than that of PGV magnitudes. Nonetheless, the earthquake magnitudes estimated from both methods were consistent with their counterparts (Mw 7.3) reported by the United States Geological Survey (USGS). The final magnitude estimated from the PGD and PGV methods were Mw 7.25 and Mw 7.31, respectively. In addition, our results highlighted how the number of high-rate GNSS stations could influence the stability and convergence time of magnitude estimation.
Characterizing the coseismic slip behaviors of earthquakes could offer a better understanding of regional crustal deformation and future seismic potential assessments. On 18 December 2023, an Mw 6.0 earthquake occurred on the Lajishan–Jishishan fault system (LJFS) in the northeastern Tibetan Plateau, causing serious damage and casualties. The seismogenic fault hosting this earthquake is not well constrained, as no surface rupture was identified in the field. To address this issue, in this study, we use Interferometric Synthetic Aperture Radar (InSAR) data to investigate the coseismic surface deformation of this earthquake and invert both ascending and descending line-of-sight observations to probe the seismogenic fault and its slip characteristics. The InSAR observations show up to ~6 cm surface uplift caused by the Jishishan earthquake, which is consistent with the thrust-dominated focal mechanism. A Bayesian-based dislocation modeling indicates that two fault models, with eastern and western dip orientations, could reasonably fit the InSAR observations. By calculating the coseismic Coulomb failure stress changes (∆CFS) induced by both fault models, we find that the east-dipping fault scenario could reasonably explain the aftershock distributions under the framework of stress triggering, while the west-dipping fault scenario produced a negative ∆CFS in the region of dense aftershocks. Integrating regional geological structures, we suggest that the seismogenic fault of the Jishishan earthquake, which strikes NNE with a dip of 56° to the east, may be either the Jishishan western margin fault or a secondary buried branch. The optimal finite-fault slip modeling shows that the coseismic slip was dominated by reverse slip and confined to a depth range between ~5 and 15 km. The released seismic moment is 1.61 × 1018 N·m, which is equivalent to an Mw 6.07 earthquake. While the Jishishan earthquake ruptured a fault segment of approximately 20 km, it only released a small part of the seismic moment that was accumulated along the 220 km long Lajishan–Jishishan fault system. The remaining segments of the Lajishan–Jishishan fault system still have the capability to generate moderate-to-large earthquakes in the future.
23 December 2024 in Journal of the Brazilian Society of Mechanical Sciences and Engineering
Studying the relationship between coseismic slip and aseismic creep helps better understand the seismic and aseismic behavior of crustal faults. We use multi-platform synthetic aperture radar (SAR) and global positioning system data to invert for the coseismic fault slip of the 2016 Mw 6.6 Muji earthquake in western China. Our results indicate that the earthquake ruptured two asperities, which were separated by a ~ 10-km-long slip gap. InSAR observations (2014–2016) before the earthquake show two aseismic creeping sections along the Muji fault. The western creeping section overlapped with the coseismic slip gap, and the eastern creeping section marked the eastern termination of the earthquake rupture. The spatial coincidence of creep with coseismic slip gap suggests aseismic slip might arrest and act as a barrier to seismic rupture propagation. Moreover, we observe that the creep rate along the western creeping section was similar before and after (2017–2020) the earthquake, while it accelerated along the eastern creeping section after the earthquake. Creep rate acceleration along the eastern creeping section is likely to be promoted by positive Coulomb stress changes. InSAR time-series data show that the promotion has lasted several years and is perhaps long lasting, highlighting a need to reassess the aseismic slip behavior and seismic potential along creeping faults with large historical earthquakes.