9:45 AM - 10:00 AM
[HCG22-04] Distribution of small earthquakes observed in the northeastern part of the Korean Peninsula and their detection by IMS
Keywords:Comprehensive Nuclear-Test-Ban Treaty, DPRK, Earthquake, Nuclear test, International Monitoring System
From 2006 to 2017, six seismic events caused by large explosions, believed to be underground nuclear tests, were observed in northeastern North Korea. Those sixth event on September 3, 2017 was the largest one with a body-wave magnitude of 6.1. Just after the event, an earthquake was observed at the same location approximately eight minutes later, and several studies of the seismic waves currently lead to the belief that a cavity created by the large explosion collapsed. Then, 20 days later, starting on September 23, small earthquakes of up to magnitude 3 were sporadically detected around the presumed nuclear test site, where the large explosions were observed, by the Korea Meteorological Administration's (KMA) seismic observation network.
The KMA publishes earthquake catalog detected by its seismic observation network on the Korean Peninsula, and it shows that even now, more than seven years after the nuclear test in 2017, small earthquakes have been detected around the presumed nuclear test site (https://www.weather.go.kr/w/eqk-vol/recent-eqk.do). In addition, some of the earthquakes detected by KMA were also detected by the CTBT (Comprehensive Nuclear-Test-Ban Treaty) observation network (IMS: International Monitoring System).
According to previous studies, these earthquakes are estimated to have tectonic focal mechanisms, different from the explosion in 2017 and the earthquake following about 8 minutes later, based on analysis of observed waveforms from nearby seismic observation stations.While IMS is designed to detect underground nuclear tests of 1 kt or more (roughly corresponding to earthquakes of magnitude 4 or more on the body-wave magnitude), these earthquakes are very small in scale. Therefore, seismic signals from those events have only been observed at the IMS stations in the nearest locations, Ussuriysk (Russia) or Wonju (South Korea) in most cases, however, the waveforms tend to show different aspect from those of the previous six explosion events.
In this presentation, based mainly on the origin information published by KMA, we will report on the distribution of hypocenters around the presumed nuclear test site, their time series variation, the characteristics of the observed waveforms, and their detection by IMS.
The KMA publishes earthquake catalog detected by its seismic observation network on the Korean Peninsula, and it shows that even now, more than seven years after the nuclear test in 2017, small earthquakes have been detected around the presumed nuclear test site (https://www.weather.go.kr/w/eqk-vol/recent-eqk.do). In addition, some of the earthquakes detected by KMA were also detected by the CTBT (Comprehensive Nuclear-Test-Ban Treaty) observation network (IMS: International Monitoring System).
According to previous studies, these earthquakes are estimated to have tectonic focal mechanisms, different from the explosion in 2017 and the earthquake following about 8 minutes later, based on analysis of observed waveforms from nearby seismic observation stations.While IMS is designed to detect underground nuclear tests of 1 kt or more (roughly corresponding to earthquakes of magnitude 4 or more on the body-wave magnitude), these earthquakes are very small in scale. Therefore, seismic signals from those events have only been observed at the IMS stations in the nearest locations, Ussuriysk (Russia) or Wonju (South Korea) in most cases, however, the waveforms tend to show different aspect from those of the previous six explosion events.
In this presentation, based mainly on the origin information published by KMA, we will report on the distribution of hypocenters around the presumed nuclear test site, their time series variation, the characteristics of the observed waveforms, and their detection by IMS.