Resolving Sub-Kilometer Cascading Ruptures of Moderate Earthquakes With Distributed Acoustic Sensing

Abstract

A comprehensive understanding of earthquake dynamics requires integrated observations of both low-frequency slip and high-frequency energy radiation. Although back-projection is a powerful technique for tracking these high-frequency signals, its application to moderate earthquakes remains constrained by the sparse station density of conventional seismic networks. Distributed Acoustic Sensing (DAS) offers a promising complement by providing dense and continuous measurements along existing fiber-optic cables. In this study, we systematically evaluate the resolution capabilities of DAS networks for back-projection through synthetic tests and the analysis of an $M_W$ 4.9 earthquake in the Eastern California Shear Zone. We demonstrate that the dense spatial sampling of DAS enables the identification of fine-scale rupture features. Furthermore, we propose a two-step inversion procedure that integrates DAS observations with regional broadband station data. Our results suggest that DAS arrays can significantly enhance the spatiotemporal resolution of earthquake observation systems and improve our understanding of rupture dynamics and seismic risk.