Geophysics and Geophysical Exploration (지구물리와물리탐사)

Korean Society of Earth and Exploration Geophysicists (한국지구물리·물리탐사학회)
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A marine deep-towed DC resistivity survey in a methane hydrate area, Japan Sea

동해의 메탄 하이드레이트 매장 지역에서의 해양 심부 견인 전기비저항 탐사

  • Goto, Tada-Nori (Japan Agency for Marine-Earth Science and Technology (JAMSTEC)) ;
  • Kasaya, Takafumi (Japan Agency for Marine-Earth Science and Technology (JAMSTEC)) ;
  • Machiyama, Hideaki (Japan Agency for Marine-Earth Science and Technology (JAMSTEC)) ;
  • Takagi, Ryo (Japan Agency for Marine-Earth Science and Technology (JAMSTEC)) ;
  • Matsumoto, Ryo (Department of Earth and Planetary Science, University of Tokyo) ;
  • Okuda, Yoshihisa (National Institute of Advanced Industrial Science and Technology (AIST), Geological Survey of Japan (GSJ), Institute for Geo-Resources and Environment (GREEN)) ;
  • Satoh, Mikio (National Institute of Advanced Industrial Science and Technology (AIST), Geological Survey of Japan (GSJ), Institute for Geo-Resources and Environment (GREEN)) ;
  • Watanabe, Toshiki (Research Center for Seismology, Volcanology and Disaster Mitigation, Graduate School of Environmental Studies, Nagoya University) ;
  • Seama, Nobukazu (Research Center for Inland Seas, Kobe University) ;
  • Mikada, Hitoshi (Department of Civil and Earth Resources Engineering, Graduate School of Engineering, Kyoto University) ;
  • Sanada, Yoshinori (Japan Agency for Marine-Earth Science and Technology (JAMSTEC)) ;
  • Kinoshita, Masataka (Japan Agency for Marine-Earth Science and Technology (JAMSTEC))
  • 후등충덕 (일본 해양연구개발기구) ;
  • 립곡귀사 (일본 해양연구개발기구) ;
  • 정산영장 (일본 해양연구개발기구) ;
  • 고목량 (일본 해양연구개발기구) ;
  • 송본량 (동경대학 기술 및 천문학과) ;
  • 오전의구 (일본 산업기술종합연구소 지구자원환경연구부문) ;
  • 좌등간부 (일본 산업기술종합연구소 지구자원환경연구부문) ;
  • 도변준수 (나고야 대학, 환경대학원, 지진, 화산 및 재난 방재 연구 센터) ;
  • 도신화 (고베 대학, 내륙해 연구 센터) ;
  • 진전가전 (교토대학, 공학연구과 사회기반공학) ;
  • ;
  • 목하정고 (일본 해양연구개발기구)
  • Published : 2008.02.29
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Abstract

We have developed a new deep-towed marine DC resistivity survey system. It was designed to detect the top boundary of the methane hydrate zone, which is not imaged well by seismic reflection surveys. Our system, with a transmitter and a 160-m-long tail with eight source electrodes and a receiver dipole, is towed from a research vessel near the seafloor. Numerical calculations show that our marine DC resistivity survey system can effectively image the top surface of the methane hydrate layer. A survey was carried out off Joetsu, in the Japan Sea, where outcrops of methane hydrate are observed. We successfully obtained DC resistivity data along a profile ${\sim}3.5\;km$ long, and detected relatively high apparent resistivity values. Particularly in areas with methane hydrate exposure, anomalously high apparent resistivity was observed, and we interpret these high apparent resistivities to be due to the methane hydrate zone below the seafloor. Marine DC resistivity surveys will be a new tool to image sub-seafloor structures within methane hydrate zones.

해양 심부 견인 전기비저항 탐사 방법이 새로이 개발되었다. 이 방법은 탄성파 반사법 탐사에서 잘 영상화 되지 않던 메탄 하이드레이트의 상부 경계를 찾아내기 위해 고안되었다. 이 장비는 하나의 송신기와 8개의 송신 전극들 및 한 개의 수신쌍극자를 갖는 160 m 연장의 긴 꼬리가 연구용 탐사선에 연결 되어 해저면 근처에서 끌리도록 만들어져 있다. 수치모형실험은 고안된 해양 전기비저항 탐사 방법이 메탄 하이드레이트 층의 상부를 효과적으로 잘 영상화함을 보여주었다. 실제 탐사는 메탄 하이드레이트가 노두로 관찰된 동해에 속해 있는 Joetsu의 먼바다에서 수행되었다. 대략 3.5 km에 달하는 탐사측선에 대하여 전기비저항 자료가 성공적으로 얻어 졌으며 상대적으로 높은 겉보기비저항 값들이 감지되었다. 특별히 메탄 하이드레이트가 들어나 있는 지역에서는 이상적으로 높은 겉보기비저항 값이 관측되었으며, 우리는 이 고겉보기비저항 값이 해저면 밑의 메탄 하이드레이트 지역에 의한 것으로 해석 하였다. 해양 전기비저항 탐사는 메탄 하이드레이트가 매장되어 있는 지역에서 해저면 하부를 잘 영상화 할 수 있는 새로운 도구가 될 것이다.

Keywords

References

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