North Korea's Nuclear Test: The Capability for Seismic Monitoring of the North Korean Test Site

Abstract

On 9 October 2006 the Democratic People's Republic of Korea (DPRK) conducted an underground nuclear explosion at a test site near Kimchaek. The explosion was detected by several seismic stations in the International Monitoring System (IMS) and was also reported by the U.S. Geological Survey (USGS). The event magnitude was reported as 4.1 by the International Data Centre (IDC) in Vienna and 4.2 by the USGS. In this study we analyze the recorded waveforms at selected seismic stations in order to investigate the capability of the global seismic network to monitor the DPRK test site for possible future explosions. Our analysis is based upon the so-called site-specific threshold monitoring (SSTM) approach. Using actual seismic data recorded by a given network, SSTM calculates a continuous “threshold trace,” which provides, at any instance in time, an upper magnitude bound on any seismic event that could have occurred at the target site at that time. Let us first emphasize that a large number of seismic stations worldwide recorded this event, and that many of these stations were not analyzed as part of this study. For example, Ammon and Lay (2007) demonstrate that a number of stations in the North American USArray network, which is not part of the IMS, have excellent recordings, some of them with a high signal-to-noise ratio. Likewise, several IMS stations, e.g. in Russia and Mongolia, detected the event but the recordings were not analyzed in this study. Our main reason for not including these stations is that in a site-specific capability study of the type discussed here, the resulting threshold is dominated by a few stations of exceptionally high detection capability. We have focused our analysis on these exceptional stations. In fact, as will be shown later in this study, the monitoring capability of our selected network (nine stations) …