Time-advanced occurrence of moderate-size earthquakes in a stable intraplate region after a megathrust earthquake and their seismic properties

Sci Rep. 2018 Sep 6;8(1):13331. doi: 10.1038/s41598-018-31600-5.

Abstract

The distance-dependent coseismic and postseismic displacements produced by the 2011 MW9.0 Tohoku-Oki megathrust earthquake caused medium weakening and stress perturbation in the crust around the Korean Peninsula, increasing the seismicity with successive ML5-level earthquakes at the outskirts of high seismicity regions. The average ML5-level occurrence rate prior to the megathrust earthquake was 0.15 yr-1 (0.05-0.35 yr-1 at a 95% confidence level), and the rate has increased to 0.71 yr-1 (0.23-1.67 yr-1 at a 95% confidence level) since the megathrust earthquake. The 2016 ML5-level midcrustal earthquakes additionally changed the stress field in adjacent regions, inducing the 15 November 2017 ML5.4 earthquake. The successive 2016 and 2017 moderate-size earthquakes built complex stress fields in the southeastern Korean Peninsula, increasing the seismic hazard risks in the regions of long-term stress accumulation. The increased seismic risks may continue until the medium properties and stress field are recovered.

Publication types

  • Research Support, Non-U.S. Gov't