Fluid distribution around a seismogenic zone along a plate boundary fault imaged and monitored by controlled source electromagnetic sounding

2005财政年度，开展了3次长期监测地震带的可行性研究和试验。研制了船舶可控源电磁测量数值计算程序。在两次研究巡航中进行了海洋直流电阻率测量。分析了苏门答腊岛大地震余震的地震记录。这些研究有助于海底电缆长期电磁力仪和海底地震仪的新发展和改进。2006财政年度，在一个小水池中对这些海底仪器进行了水下试验。另外，位于东海大地震带上的离丰桥的电缆是用电缆船拉起的，并在电缆末端安装了连接装置。2007财年，新开发的海底仪器连接到off Toyohashi电缆末端的连接单元。JAMSTEC船和ROV用于海底作业。因此，一个多学科、能力更强的观测站在丰桥附近建成，正好位于东海大地震带上，其目标是海底地震、地壳变形和海底以下的地下水流动。从离丰桥海底电缆同时发送连续的人工电信号，从而开始了对海底以下电导率变化的第一次海底监测。在进行海底连续监测之前，对东海特大地震带周边的地壳电导率结构进行了海洋大地电磁测量。12个仪器成功部署和回收。得到的数据集显示了俯冲菲律宾海板块的导电性结构。结果，通过这个项目发表了几篇论文和报告，涉及电缆观测站，海洋控制源电磁测量和海底地下水流可能激发的电磁现象。少

In FY 2005, we carried out three feasibility studies and tests for long term monitoring of seimogenic zone. A numerical calculation codes for marine controlled source electromagnetic survey was developed. Marine DC resistivity surveys were conducted at two research cruises. Seismic records of aftershocks of the Sumatra great earthquakes were analyzed. These studies are helpful for new development and refinement of cabled long-term ocean bottom electromagnetometers and ocean bottom seismometers. In FY 2006, underwater tests for these ocean bottom instruments were carried out in a small pool. Also, the off-Toyohashi cable, located on the Tokai mega-earthquake zone, was pulled up by using a cable ship and was deployed after attaching a junction unit to the end. In FY 2007, the newly developed ocean bottom instruments were connected to the junction unit at the end of off Toyohashi cable. The JAMSTEC vessels and a ROV were used for the seafloor operations. As a result, a multidisciplinary c … More abled observatory, whose targets are submarine earthquakes, crustal deformation and groundwater flow below the seafloor, was constructed off-Toyohashi, just on the Tokai mega-earthquake zone. Continuous artificial electric signals are sent from the off-Toyohashi cable simultaneously, so that the first ocean bottom monitoring of electrical conductivity variation below the seafloor was started.Before the continuous seafloor monitoring, marine magnetotelluric surveys were carried out off-Toyohashi area to image the crustal electrical conductivity structure around the Tokai mega-earthquake zone. Twelve instruments were deployed and recovered successfully. The obtained data set show us the conductivity structure of subducting Philippine Sea plate.As a result, several papers and presentations were presented through this project, relating to the cabled observatory, marine controlled source electromagnetic survey and electromagnetic phenomena possibly excited by groundwater flow below the seafloor. Less