Joint inversion of strain and tilt data using the Akaike\u2019s Bayesian information criterion to map detailed slip distributions of short-term slow slip events

Akio Kobayashi,Takahiro Tsuyuki,Reiko Kai,Satoshi Itaba,Takeshi Kimura

doi:10.1186/s40623-021-01517-x

Abstract

Along the Nankai Trough subduction zone, southwest Japan, short-term slow slip events (SSEs) are commonly detected in strain and tilt records. These observational data have been used in rectangular fault models with uniform slip to analyze SSEs; however, the assumption of uniform slip precludes the possibility of mapping the slip distribution in detail. We report here an inversion method, based on the joint use of strain and tilt data and evaluated in terms of the Akaike’s Bayesian information criterion (ABIC), to estimate the slip distributions of short-term SSEs on the plate interface. Tests of this method yield slip distributions with smaller errors than are possible with the use of strain or tilt data alone. This method provides detailed spatial slip distributions of short-term SSEs including probability estimates, enabling improved monitoring of their locations and amounts of slip.

Highlights

Several types of slow earthquakes commonly occur along the Nankai Trough subduction zone (Fig. 1) of the Philippine Sea plate southwest of Japan (Obara and Kato 2016)
Short-term slow slip event (SSE) along the subduction zone of the Nankai Trough are typically detected by interpreting strain and tilt data
We formulated an inversion method to estimate the slip distribution of these SSEs by the joint use of strain and tilt data based on Akaike’s Bayesian information criterion (ABIC)

Summary

Introduction

Several types of slow earthquakes commonly occur along the Nankai Trough subduction zone (Fig. 1) of the Philippine Sea plate southwest of Japan (Obara and Kato 2016). Hirose and Kimura (2020) used tilt-offset measurements to estimate slip distributions of short-term SSEs from January 2001 to March 2019 in the Shikoku region and gain insight into the slip budget along the strike direction of the Nankai Trough. These estimates of the slip distribution on the plate boundary surface yield more detailed slip locations than rectangular fault models, they employed GNSS or tilt data alone. We report the use of this method to calculate detailed spatial slip

Methods

Results

Conclusion