Analysis of newly-detected small seismic events in and near the Northern Korean Peninsula from 2004 to 2010: Part I, correlation, detection, and relative locations

Abstract

We have detected and located 1,015 seismic events observed at 4 or more stations of the 17-station Dongbei Broadband Seismographic Network (DBN), which operated from June 2004 to September 2010 in Northeast China near the border with the Democratic People’s Republic of Korea (DPRK). We chose 447 master seismic events reported in catalogs published by the International Seismological Centre (ISC), the Korean Meteorological Agency (KMA), the Earthquake Administration of the Jilin Province of China. Using Lg wave-trains of the master events we searched the continuous archive recorded by DBN to detect (via cross-correlation) events similar to the master events. The relative locations of this event-catalog have 95% confidence errors of only 140 m on average. The improvement in locations (compared to the starting locations) can be measured by a factor of 95 reduction in the average standard deviation of the residuals, and by a one to two orders of magnitude reduction in scatter of the double-difference locations as measured by average inter-event separation distance. The natural seismicity rate is lower for this broad area of interest in and near North Korea than for California and China and other seismically-active regions. But it is much higher than was expected for what was previously thought of as a generally aseismic region. This is important to know and recognize for nuclear monitoring – and is important too for an understanding of the distribution of stresses in regions where significant seismic events turn out to have unsuspected low-magnitude aftershocks.