Forensic seismologiy for an underwater explosion vis- à-vis the ROKS Cheonan Sinking

Abstract

For a very shallow underwater explosion, spectral analysis is preferable to cepstral analysis to find characteristics of a bubble pulse and reverberation effects. Time-domain analyses show bubble pulses and bubble jets as well as positive polarities of the first P-wave arrivals on the vertical component, and spectral analyses also clearly reveal the bubble pulse and reverberation effects. 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. The findings of a bubble jet and a toroidal bubble deformation including a bubble pulse are highlighted 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 using the seismological analyses and boundary element method. The 136 kg TNT is equivalent to one of the abandoned land control mines (LCM) that were deployed near the Northern Limited Lines (NLL) in the Yellow Sea by the South Korean Navy in the late 1970s.