[M-AG40] CTBT IMS Technologies for Detecting Nuclear Explosion and Their Applications to Earth Science

[MAG40-03] Waveform Analysis on Induced Earthquakes after the 2017 Nuclear Test and Detected Mining Events in DPRK

*Masashi Motohashi¹, Takanari Fujii¹, Takayuki Otsu¹ (1.Japan Weather Association)

Keywords:Waveform Analysis, Event Discrimination, Nuclear Test, Induced Earthquake

After the DPRK September 2017 nuclear test event, several earthquakes were occurred near the test site. The scale of these induced earthquake events was fairly very small, therefore there were a few CTBT IMS seismic stations (e.g. KSRS, USRK, KLR) which could detect earthquake signals. Japan NDC-1 (National Data Center-1) tried to locate and discriminate these events utilizing non-IMS data such as IRIS (Incorporated Research Institutions for Seismology).

Analyzing waveform data of these events, S-wave (Sn, Lg-Phase) amplitude of waveform at close stations is larger than that of P-wave (Pn, Pg-Phase) and the feature of these events is presumed to be natural earthquake rather than man-made explosion. Near the DPRK test site, there are two open-pit mines at Chung-gang city and Musan city which locates DPRK-China border. We also compared with past mining explosion event there and we discriminated events with the indexes such as regional P/S ratio, P/S Spectral Ratio.

It was quite difficult to make event discrimination using only IMS seismic waveform data. IMS seismic network is not designed for detecting small-scale nuclear test far less than 1kt. Therefore, local and non-IMS seismic network data could largely contribute to refine event location and event discrimination.