Analysis of newly-detected small seismic events in and near the Northern Korean Peninsula from 2004 to 2010: Part II, absolute locations, origin times, and event identification

Abstract

We detected, located, analyzed and identified new seismic events from continuous waveforms of the 17-station Dongbei network (DBN) from June 2004 to September 2010 in Northeast China near the border with North Korea. We used 447 master events from the International Seismological Centre (ISC), the Korean Meteorological Agency (KMA), and Jilin Province of China catalogs to detect more events using Lg waves. 1,015 located events were comprised of 140 similar event clusters. About 40% of the events are from 9 earthquake clusters in NE China; 20% of the events were associated with 10 clusters of earthquakes and mining explosions around Pyongyang, North Korea; and nearly 10% of the events are clustered around the east coast of South Korea. The last clusters are remarkable in that master events with magnitude less than 2.0 were used to detect and locate repeating events at a distance 400–500 km away from the 500 km long linear array of stations trending ~ 60º (DBN). Clusters with 95% of their origin times occurring primarily during working hours and working days are likely mining explosions. The binomial test shows as much as 22% to 39% of the detected catalogs verified at 2, 3, and 4 or more stations and six of the nine largest located clusters can be identified as statistically significant explosion clusters. Correlation detectors find large numbers of similar events that can be identified as aftershocks (following Omori’s law), and mining explosions. These methods provide complementary, independent evidence for event identification down to remarkably low magnitude.