Location and source characteristics of North Korea’s 2017 nuclear test and its triggered seismicity
Event Type: Seminar
Event Date: 14 September 2018 - 4:00pm to 5:00pm
Venue: ASE 3D Viz Laboratory Room (N2-B1c-16c)
Speaker: Dr. Jiayuan Yao
About the speaker:
Jiayuan Yao is a research fellow at School of Physical and Mathematical Sciences in Nanyang Technological University. He received his Ph.D. (2018) and B.Sc. (2012) in Geophysics from University of Science and Technology of China. His primary research areas are the structure of the Earth's interior and seismic monitoring. He has published six academic articles at JGR, GRL, SRL, PEPI, et al., with five of them as the first-author. He is also a peer-reviewer of the scientific journal, Seismol. Res. Lett. (2).
About the event:
On 3 September 2017, the Democratic People’s Republic of Korea (North Korea) announced that it had successfully conducted a thermonuclear test (hydrogen bomb). Unlike North Korea’s previous tests, the 2017 test is different in several aspects: 1) it appears to be the largest to date, with a magnitude ranging from 5.6 to 6.3, 2) it was followed by a series of small seismic events in the region and 3) it generated significant surface disturbance that was visible from the satellite imagery and InSAR data. Three questions were then raised: 1) What are the location and source process of the 2017 test? 2) What are the locations and source mechanisms of those small seismic events? 3) What are the relationship between the test and those small seismic events? We tried to resolved those questions based on high-quality seismic observations. North Korea’s 2017 test and its previous tests since 2009 were first jointly relocated to be beneath Mount Mantap. During several seconds after the detonation of the nuclear device of the 2017 test, the test generated a prompt source medium damage expanding away from the test center mostly along the direction of 320°, and those deformed surrounding rocks collapsed toward the test center along the weakness direction in an opposite way 8.5 minutes later. The later process was represented by a near vertical on-site collapse toward the nuclear test center from 440±260 m northwest of the nuclear test site, which was previously reported to be a small seismic event with a magnitude of 4.1. Other small seismic events were inferred to be earthquakes within a region of 2 km, ~8.4 km north of the test site, which were triggered by the test and lasted for at least eight months. The first aftershock occurred 6 hours after the explosion, while two earthquake bursts occurred three and five months after the test and lasted for several days. The occurrence of the on-site collapse calls for continued monitoring of any leaks of radioactive materials from the test site. The triggered earthquake swarm indicates that North Korea’s past tests have altered the tectonic stress in the region to the extent that previously inactive tectonic faults in the region have reached their state of critical failure.