Precise Estimation of Source Parameters Using Distributed Acoustic Sensing Data in Central Shikoku, Japan

Abstract

Distributed acoustic sensing (DAS) can provide high-density spatial measurements, enabling precise estimates of the source parameters of earthquakes. We analyzed nine small earthquakes in central Shikoku, Japan, using DAS observations obtained from two nearby fiber-optic cables with different orientations. Differential travel times measured by waveform cross-correlation enabled high-precision hypocenter relocation. The relocated hypocenters were substantially shallower than those reported in the catalog of the Japan Meteorological Agency. Eight of the nine relocated earthquakes formed a compact cluster; seven of these were aligned along a northwest-dipping structure consistent with a major geological boundary. We also applied the empirical Green’s function method to P-wave DAS data and estimated corner frequencies after evaluating their spatial variation across the focal sphere. The resulting stress-drop estimates ranged from 0.6 to 2 MPa. Compared with conventional seismic stations, the dense DAS observations yielded smoother spectral ratios and better-constrained source parameters. These results demonstrate the potential of DAS for high-precision characterization of microearthquake locations and source properties.