Long-period surface motion of the multi-patch Mw9.0 Tohoku-Oki earthquake

TL;DR

This study demonstrates the ability to capture long-period surface motions from the Tohoku-Oki earthquake using PPP, revealing large ground motions in Japan's sedimentary basins and suggesting a multi-patch rupture model.

Contribution

It introduces a method to analyze long-period ground motions using PPP and compares geodetic data with GMPE, providing new insights into the earthquake's rupture complexity.

Findings

Long-period motions (>3s) are well captured and significant in sedimentary basins.

Spectral Acceleration estimates align with predictions for distances 100-500km.

Evidence suggests the earthquake involved multiple rupture patches.

Abstract

We show that it is possible to capture the oscillatory ground motion induced by the Tohoku-Oki event for periods ranging from 3 to 100s using Precise Point Positioning (PPP). We find that the ground motions of the sedimentary basins of Japan were large (respectively > 0.15m/s and >0.15m/s2 for velocity and acceleration) even for periods larger than 3s. We compare geodetic observables with a Ground Motion Prediction Equation (GMPE) designed for Japan seismicity and find that the Spectral Acceleration (SA) is well estimated for periods larger than 3s and distances ranging from 100 to 500km. At last, through the analysis of the displacement attenuation plots, we show that the 2011 Tohoku-Oki event is likely composed of multiple rupture patches as suggested before by time-reversal inversions of seismic data.