Spatial and Temporal Characteristics of Seismicity After North Korea’s 3 September 2017 Nuclear Test

Abstract

Following North Korea’s sixth nuclear test in 2017, a series of small seismic events occurred around the Punggye-ri nuclear test site. Using continuous waveform data from 2016 to 2024, we employed the match-and-locate method and detected 647 new seismic events around the test site. These detected events all exhibit similar waveform characteristics, which are significantly different from the waveforms of the nuclear test and the collapse event. Statistical results indicate that seismic activity increased significantly near the nuclear test site after the sixth nuclear test on 3 September 2017. The magnitudes of these seismic events primarily range from 1.5 to 2.5. In September 2021 and February 2022, the frequency of such events exceeded 30 occurrences per month. Using the double-difference earthquake relocation algorithm (hypoDD) and the bootstrap method, we obtained precise locations for 491 seismic events and analyzed their location uncertainty. The relocated seismic events exhibit a north-northwest–south-southeast distribution trend. Most events are concentrated in the north and northwest of the test site, 4–9 km away. From 2017 to 2024, the seismic events show a trend of migrating southeastward toward the test site.