SGER - Hydrologic Monitoring of Leaking Coseismically Active Thrusts: A Pilot Study in the Nankai Subduction Zone

【摘要】本项目将在日本南开吸积楔进行构造与水文地质相互作用的初步研究。这项研究需要部署五种仪器，在一年的时间里监测沿主要同震活动逆冲带（OOST）的冷渗漏。pi已被邀请参加为期三周的日本巡航，以调查渗漏并部署仪器。这些逆冲直接连接到发震带，已知会泄漏流体，并且沿着它们已经发现了许多渗漏。最近的观测表明，这一东部地区也是极低频地震（VLF）的发源地，这种地震可能与发震带上倾极限附近的超慢地震有关。pi将使用的仪器已被证明能够收集活跃渗漏环境中流体流动、温度、水化学和气体化学的长期记录。通过将这些流动记录与附近的钻孔地震记录（可能还有日本OBS记录）进行比较，pi希望澄清地下流体压力脉冲与与VLF事件相关的应力释放事件之间的关系。本研究的广泛影响主要来自于它与主要国际研究和减轻自然灾害项目的直接关联。该区域是IODPs NantroSeize钻井项目的重点区域。它还旨在帮助启动美国和日本科学家之间的高度合作伙伴关系。最终，我们将使用的仪器可以联网，作为长期监测系统的一部分。研究发生地震和海啸的俯冲带的断层不稳定性具有直接的人类和政治影响。

AbstractUnder this award, the PIs will undertake a pilot study of the interaction of tectonics and hydrogeology at the Nankai accretionary wedge of Japan. The study entails the deployment of five instruments for one year monitoring of cold seeps along the major coseismically active out-of-sequence thrust (OOST) zones. The PIs have been invited on a 3-week Japanese cruise that will investigate the seeps and deploy the instruments. These thrusts link directly down to the seismogenic zone, are known to leak fluids, and numerous seeps have been identified along them. Recent observations indicate that this OOST region is also the location from which very low frequency (VLF) earthquakes appear to be originating that may be tied to ultra slow earthquakes near the updip limit of the seismogenic zone. The PIs will be using instrumentation that has been shown to be capable of collecting long-term records of fluid flow, temperature, and both aqueous and gas chemistry in active seep environments. By comparing these flow records to nearby borehole seismic records (and perhaps Japanese OBS records), The PIs hope to clarify the relationship between subsurface fluid pressure pulses and stress release eventsrelated to the VLF events.The broader impacts of this study come primarily through its direct relevance to major international programs of research and natural hazard mitigation. The field area is the focus of a significant portion of IODPs NantroSeize drilling program. It is also intended to help initiate a highly collaborative partnership between US, and Japanese scientists. Eventually, the instrumentation we will be using can be networked as part of a long-term monitoring system. Studying fault instabilities in an earthquake and tsunami generating subduction zone has direct human and political impact.