Reexamination confirming additional seismic evidence for the 12 May 2010 low-yield nuclear test

Abstract

This study examines event location and source discrimination for the May 12, 2010 possible nuclear event in North Korea, using seismic data recorded in the Dongbei Broadband Seismic Network in China. Using highly similar Pg waveforms between the events, we locate the event within 2 ​km of the 2009 nuclear test site. For event classification, we first build a group of reference earthquakes and explosions through a machine-learning phase picker and an event association/location process, with open-access satellite image verification; we then classify the event based on the Pg/Lg spectral ratios and Pg waveform similarity comparisons with past nuclear tests. The event is classified as a small explosion reaffirming the findings of Zhang and Wen (2015a). Along with independent scientific evidence from radionuclide studies and infrasound signal analysis, the May 12, 2010 event can be reasonably attributed to a low-yield nuclear test. Our study shows that explosion discriminants are dependent on event magnitudes and seismic noises, and vary from station to station. Accordingly, event classification should be performed on a station-by-station basis. The approach presented here is useful for seismic monitoring of low-yield nuclear tests.