동해 울릉분지에 분포하는 가스 하이드레이트 층의 특성 연구

Abstract

To identify the distribution and to interpret the characteristics of the gas hydrate layers in the Ulleung Basin, we have surveyed and gathered the multi-channel seismic data, Chirp sub-bottom profiler, SeaBeam, and 12 m piston core samples since 1996. In previous works, high-resolution seismic profiles show acoustic anomalies such as acoustic turbidity, acoustic void and pock mark which indicate the presence of gas-charged sediments. The patterns of horizontal degassing cracks originated from free methane expansion is the strong indicator of shallow gas-charged sediments in the 12 m piston core samples. The observation of submarine slides and slumps from destabilizing the sediments in the southern part of the Ulleung Basin may also point out that the gas had been released from gas hydrate dissociation during lowstand sea-level. The multi-channel seismic data show BSR, blanking, phase reversal and trapped free gas. The gas hydrate layers above which large-scale shallow gases are distributed exist at the depth of about 200 m from the sea-floor with water depth of 2,050 m. From the interpretation of seismic sections in the southern Ulleung Basin, gas hydrate layer exists in the Pleistocene-Holocene age. Therefore, gas-charged sediments, acoustic anomalies and BSR may be related to the existence of gas hydrate zone in the study area.