Forensic seismology vis-à-vis an underwater explosion for the Roks Cheonan sinking in the Yellow Sea of the Korean Peninsula

Abstract

Most underwater explosions show characteristics of a bubble pulse and reverberation effects. To specifically identify the cause of an underwater explosion, it is most important to find a bubble pulse and reverberation effects using spectral and cepstral analyses. For a very shallow underwater explosion, spectral analysis is preferable to cepstral analysis. Time-domain analyses show bubble pulses as well as positive polarities of the first P-wave arrivals on the vertical component, and frequency-domain spectral analyses also clearly reveal the bubble pulse and reverberation effects. This study includes comparative studies including a Russian underwater nuclear explosion and US Navy shock trials. The ROKS Cheonan sinking was a shallow underwater explosion that occurred near the surface showing a bubble jet characteristic resulting in splitting the ship into two pieces including a bubble pulse and reverberation effects. The findings of a bubble jet and a toroidal bubble deformation including a bubble pulse are highlighted for a shallow underwater explosion in this study. The ROKS Cheonan sinking took place off the Baengnyeong Island in the Yellow Sea of the Korean Peninsula at a depth of about 8 m in the sea depth of 44 m on March 26, 2010. The explosive charge weight was estimated at 136 kg TNT which is equivalent to one of the abandoned land control mines (LCM) that were deployed near the Northern Limited Lines (NLL) in the Yellow Sea in the late 1970s.