Acoustic Wave Signatures of Earthquake Rupture Dynamics in the Upper Atmosphere

Abstract

We perform three‐dimensional coupled earthquake‐atmosphere numerical simulations that integrate dynamic rupture, seismic wave propagation, and a compressible nonlinear atmospheric model to investigate how earthquake source parameters influence acoustic wave (AW) characteristics at 100–300 km altitude in the thermosphere. Specifically, we examine the effects of magnitude, fault type, and rupture speed by simulating a range of rupture scenarios, including sub‐ and supershear ruptures, normal and thrust faulting, heterogeneous ruptures, and tsunami earthquakes. Supershear ruptures generate AWs with earlier arrival times and distinctive signal shapes compared to subshear events. Normal‐faulting earthquakes produce much weaker AW amplitudes due to rarefaction waves at the surface evolving into shock N‐waves, contrasting with the stronger compressive AWs from thrust earthquakes. Fault heterogeneity strongly affects AWs in the lower atmosphere, but its influence diminishes in the upper atmosphere. Tsunami earthquakes yield AWs with similar periods but 20%–50% smaller amplitudes than thrust earthquakes of the same moment magnitude, offering a potential diagnostic feature. Our results show that the nonlinear evolution of AWs precludes straightforward comparison between surface and upper‐atmosphere signals, making proper modeling of upper‐atmospheric shock properties essential for reliable interpretation. We further corroborate that energy magnitude of an earthquake, rather than moment magnitude, primarily controls AW amplitude in the upper atmosphere. These findings underscore the diagnostic potential of upper‐atmosphere observations, such as Global Navigation Satellite System signals, for constraining earthquake source characteristics, improving seismic monitoring, and advancing our understanding of earthquake‐atmosphere interactions.