Prof.  So Gu  Kim
Korea Seismological Institute,  Republic of Korea

Title: Characteristics of Underwater Explosions Analyzed through Seismic, Hydroacoustic, Infrasound, and Boundary Element Method (BEM) in Relation to the ROKS Cheonan Sinking

Abstract:

For very shallow underwater explosions, spectral analysis is preferred over cepstral analysis for identifying characteristics of a bubble pulse and the effects of reverberation. Time-domain analyses reveal a bubble pulse and a bubble jet, along with positive polarities of the first P-wave arrivals on the vertical component. Spectral analyses clearly indicate the source parameters and reverberation effects. The sinking of the ROKS Cheonan generated a bubble jet characteristic force of 191 g, causing the ship to split into two pieces, which was quickly followed by a bubble pulse. This study highlights the findings of a bubble jet, a bubble pulse, and a toroidal bubble deformation. To verify our results, the ray tracing and the boundary element method are employed. The ROKS Cheonan sank off Baengnyeong Island in the Yellow Sea of the Korean Peninsula at a depth of approximately 8 m, in a sea depth of 44 m, with 136 kg of TNT on March 26, 2010. This amount of TNT is equivalent to one of the abandoned land control mines (LCM) that the South Korean Navy deployed near the Northern Limit Lines (NLL) in the Yellow Sea during the late 1970s. Consequently, the probability that the sinking of the ROKS Cheonan was due to an LCM is 99.9999 %.

Biography:

So Gu Kim, the Director of the Korea Seismological Institute and has been a Professor of Physics and Geophysics at Hanyang University in South Korea for about 30 years. He has served as an Invited Professor at the Institute of Seismology and Volcanology at Hokkaido University in Japan and at the Graduate School of Earth and Planetary Sciences at Peking University in China. Additionally, he has been an Invited Scientist at the GFZ in Potsdam, Germany, a Visiting Professor at Hamburg University, and an Invited Professor at the University of New England in Australia. Throughout his career, he has conducted numerous research projects in geophysics, including seismology, exploration geophysics, geophysical oceanography (specifically underwater acoustics and ocean exploration), and petroleum exploration.