- © 2008 by the Seismological Society of America
On 9 October 2006 North Korea announced that it had conducted a nuclear weapons test, its first, at the Chik-tong test site in north Hamgyeong Province. It had been more than eight years since the world's last known nuclear test, carried out by Pakistan on 30 May 1998 (Wallace 1998). The North Korean event was small (4.2 mb) and occurred in a part of the world with a relatively low density of accessible (open) broadband seismometers. Therefore, it provides a nice test of the nuclear explosion monitoring capability of the open global seismic network, which is deployed and maintained primarily for the study of earthquakes.
In this study we forgo a comprehensive technical analysis and instead emphasize the extent to which openly available seismic data and related products can be used in a forensic sense to study this politically important event. Much of the material presented here was developed for a discovery-based course entitled “EAS130 Seismology of Nuclear Weapons,” which is taught to freshmen and sophomores at Saint Louis University.
EVENT DETECTION AND LOCATION
The U.S. Geological Survey (USGS) operates the National Earthquake Information Center (NEIC), a 24/7 seismic monitoring facility with global earthquake monitoring capabilities and responsibilities (see http://earthquake.usgs.gov/eqcenter/). Within or near the Korean peninsula, NEIC's sources of realtime data are Global Seismic Network (GSN) stations, cooperative stations in China, and selected stations of the International Monitoring System (IMS). Based on interstation distances, noise characteristics of individual stations, regional attenuation properties, and its association and location algorithms, NEIC estimates that its minimum automatic detection and location threshold for the Korean peninsula is approximately M 4.5–4.8 (B. Presgrave, personal communication 2006).
In the week before the North Korean event, a significant number of media outlets were reporting the possibility of a nuclear test. Consequently, NEIC staff reviewed its policy and procedures with regard …