Remotely Triggered Seismicity in the Korean Peninsula by the Great 2011 Tohoku-Oki Earthquake

Recently, remote triggering by large earthquakes receives high attention due to its potential seismic hazards. Remote triggering in active tectonic regions is well conceived by various studies. However, seismic triggering in stable intraplate regions has been rarely investigated. The Korean Peninsula is located in the far eastern Eurasian plate, and belongs to a stable intraplate region with mild seismicity. The 11 March 2011 M9.0 Tohoku-Oki earthquake provides us a unique opportunity to examine the spatial-temporal changes in seismicity of stable intraplate region. The Korean Peninsula is located at about 1200 km away from the earthquake. A small numbers of triggered earthquakes are identified at many stations in seconds to minutes after the arrival of peak surface waves from the Tohoku-Oki earthquake. The sizes of triggered earthquakes are small, allowing observation only at stations in nearby distances. The triggered signals present short P- to S-arrival times, suggesting that they are likely originated by brittle failure in shallow crust. We also study the spatio-temporal evolution of the Korean seismicity before and after the Tohoku-Oki earthquake. We observe a mild increase of average seismicity in the Korean Peninsula, particularly around the northwestern and southeastern regions, after the occurrence of the earthquake. Preliminary results suggest that both high heat flow regions and local stress concentration environments were triggered by the earthquake. However, any noticeable variations of seismicities are not observed in other large earthquakes with magnitudes greater than 8.0 around the Japanese islands. We discuss the variations of seismicity by tectonic setting. Also, the nature of triggered earthquakes in stable intraplate regions is discussed.