Hailin Du

The heterogeneous coupling distribution on subduction interface not only influences the slip distribution of megathrust earthquakes but also plays a critical role in facilitating intraplate strike-slip events. On 16 July 2025, an Mw 7.3 strike-slip earthquake struck the Shumagin segment of the Alaska Peninsula, raising questions about its seismogenic fault orientation and mechanical origin. Using artificial intelligence-enhanced detection and relocation of the seismic sequence, we constructed an east–west trending, south-dipping, curved seismogenic fault model. Joint inversion of teleseismic waveforms and Global Navigation Satellite System data reveals a predominantly sinistral strike-slip mechanism, and the rupture was confined largely beneath the subduction interface, indicating that it is an intraplate event. Together with the nearby 2020 Mw 7.6 dextral strike-slip earthquake, the two events form a conjugate fault system. We demonstrate that both earthquakes, though differing in strike direction, can be explained by the stress perturbations arising from along-strike and along-dip variations in megathrust coupling, acting in concert with the background stresses from slab pull and plate bending. These findings underscore the widespread influence of coupling heterogeneity in influencing strike-slip earthquake generation in subduction zones and call for a reassessment of related seismic hazards in regions such as the Semidi segment.

Investigating aircraft accidents is a critical and challenging endeavor in the field of aviation safety. Current practices in seismology-based air accident investigations focus on locating crash sites to aid in the search and recovery of missing aircraft. In this study, we conducted an analysis of the China Eastern Airlines Boeing 737–800 crash on 21 March 2022, by leveraging three-component seismic records acquired from a location 21 km away from the crash site, in conjunction with publicly available radar data from Flightradar24 (an online service). Our approach helps to reconstruct the flight state of the aircraft at the time of the impact by modeling the dynamics of the impact with the Earth’s surface. Through an inversion process, we successfully obtained the force–time function and determined the direction of the impact force. In addition, we conducted inquiries into the weight of the 737–800 airliner, which enabled us to estimate the speed of the aircraft at the time of the accident to be about 200–264 m/s using the momentum theorem. These results are in agreement with time of the last radar signal and the measured dive angle of the airplane, providing valuable insights into the circumstances surrounding the crash.