Geophysics and Geophysical Exploration (지구물리와물리탐사)

Korean Society of Earth and Exploration Geophysicists (한국지구물리·물리탐사학회)
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Seismic Evidence and Characteristics of Gas Hydrate in the Ulleung Basin

탄성파 자료에서 나타난 울릉분지내 가스수화물의 증거와 특성

  • Published : 2008.05.31
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Abstract

Multichannel seismic profiles reveal a strong bottom simulating reflector (BSR) occurring below the seafloor in the plain of the Ulleung Basin, East Sea (Japan Sea). The essential characteristics of the BSR include its cross-cutting relationship to strata, strong amplitude, and reverse polarity with respect to the seafloor reflection, representing the base of the gas hydrate stability zone (BHSZ). The BSR reflection coefficient ranging from -0.23 to -0.26 is 1.5${\sim}$1.7 times that of the seafloor reflection and interval velocities decrease to less than 700 m/s below the BSR. These features indicate the existence of free gas beneath the GHSZ. Heat flow, estimated from the BSR depth as $95{\sim}98mW/m^2$, is in good agreement with measured values. Therefore, the BSR can be efficiently used to estimate regional distribution of heat flow in the Ulleung Basin.

동해에서 얻은 다중채널 탄성파 프로파일에서 울릉분지의 해저평원에 강한 bottom simulating reflector (BSR)가 해저면에서 왕복주시로 약 210 ms 아래에 존재하는 것을 볼 수 있다. 이 BSR은 주변의 층서를 자르고 진폭이 매우 크며 해저면 반사신호에 대해 극성이 반대이므로 가스수화물 안정영역의 기저(BHSZ)를 나타낸다고 볼 수 있다. BSR의 반사계수는 -0.23에서 -0.26으로 매우 높은데 해저면 반사계수의 1.5${\sim}$1.7배이며 그 아래 구간속도가 800 m/s 이하로 감소한다. 이러한 특징은 BHSZ 아래에 가스가 존재하는 것을 지시한다. BSR의 깊이로부터 추정한 지열은 $95{\sim}98mW/m^2$로서 지금까지 측정된 값과 잘 일치한다. 따라서 BSR은 울릉분지에서 광역적인 지열의 분포를 추정하는 데에 유용하게 쓰일 수 있다.

Keywords

References

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