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

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.

SUBMITTER: Hong TK 

PROVIDER: S-EPMC6127306 | biostudies-other | 2018 Sep

REPOSITORIES: biostudies-other