Characteristics of BSRs in the South Shetland Continental Margin, Antarctica

Abstract

In the South Shetland Continental margin, many geophysical and geological evidences indicate the existence of the buried gas hydrates. In spite of many indirect evidences, no hydrates have been recovered yet. One of the strong evidences supporting for the existence of gas hydrates is Bottom Simulating Reflector (BSR), which has a strong reflectivity and a reverse polarity. In this study we conducted multichannel seismic survey to find more seismic evidences, characteristics, and a distribution of buried gas hydrates in the South Shetland Continental margin. In 2008 and 2009, we have conducted 2D and pseudo-3D seismic surveys using a 12-channel seismic system. 2D seismic profiles show strong BSRs on the continental slope. BSRs are found in between 61° and 62° S and between 56° and 59° W. These are also found in the depth range of from 1,000 to 5,000 m. We estimated the area of BSR as 3,600 km2 by analyzing Korea and international seismic data. To investigate detailed structures of BSR surfaces in a highly probable area of gas hydrates, we acquired thirty four 2-D seismic lines with interval of 200 meters. The BSR reflection coefficients are calculated using the reflection amplitudes measured from the seafloor, multiple and BSR. Around local topographic highs, BSRs show strong reflectivity and their reflection coefficients have values of between 0.25 and 0.35.