Spatial variation of shear‐wave splitting across an active fault and its implication for stress accumulation mechanism of inland earthquakes: The Atotsugawa fault case

Abstract

We analyzed shear‐wave splitting of small earthquakes around the Atotsugawa fault, central Japan, to infer a spatial variation in the direction of maximum horizontal compression (Shmax). While the angle, ϕ, between the Shmax direction and fault strike ranges approximately from 55° to 80° at the stations 2 to 8 km from the fault, it approaches 45° at the stations within 1 km from the fault. The present result indicates the local stress accumulation due to the localized flow or slip along the deep extension of the fault. The Finite Element Modeling of the stress field around the fault suggests that the present existing stress field can be explained by the superposition of the stress field associated with regional deformation and the stable slip along the deep extension of the fault.