Interlacing ruptures of the 2024 Wushi Mw 7.0 earthquake (Chinese Tian Shan) revealed by dense seismic array observations

The 22 January 2024 Mw 7.0 Wushi earthquake (WSEQ) struck the Wushi Basin along the southern margin of the Tian Shan, Xinjiang, China. As the largest earthquake in the region since the 1992 Mw 7.3 Suusamyr earthquake (Kyrgyzstan), the WSEQ is among the few large earthquakes captured by high-quality observational datasets—including the earthquake early warning network operated by China Earthquake Administration before and a dense temporary seismic array deployed immediately after the mainshock in the Tian Shan region. This provides a rare opportunity to investigate fault network activation and rupture behavior in the tectonically active southern Tian Shan.

We picked and associated Pg/Sg phases using a neural network and the REAL method, respectively, followed by relocating all events via NonLinLoc and the double-difference relocation method. Focal mechanisms were also determined for aftershocks with M ≥4.

Our results are as follows: 1) The seismogenic fault of the WSEQ strikes northwest, correponding to a moderately-dipping, oblique-reverse main-fault rupture; 2) The mainshock triggered reactivation of a series of small-scale faults, and aftershock distribution is closely linked to these active faults in the study area; 3) Aftershocks are concentrated on subfaults rather than the main fault; and a shallowly buried subfault produced distinct surface rupture whereas the main fault is completely blind. This fault network, misaligned with the prevailing background stress field, likely forms through a reactivation of inherited weak planes.

These results illustrate that structural inheritance strongly controls fault geometric architecture and underscores the complexity of seismic activity and rupture behavior within the active fault network.