NanTroCORK: Development of hydrologic long-term CORK observatories in the seismogenic Nankai Trough subduction zone, Japan

IODP已经开始了复杂的钻探项目“NantroSEIZE”（南开海槽地震带实验），这是一个多阶段的努力，在日本近海的俯冲巨型逆冲断层中钻探7个地点的断面。NanTroSEIZE的一个基本目标是建立一个分布式的长期观测网络，覆盖下至孕震区上倾极限的传入板块。在这里，我们建议安装在两个钻井现场，这是由高应变和快速脱水的前弧俯冲系统。在这些地点，孔隙压力（作为应变的代理）和温度将在沉积物的增生楔和俯冲序列，以及在其等效的进一步向上倾斜进行监测。选定的地点是特别重要的监测，因为他们的位置在上覆欧亚板块（NT 1-03）和下行菲律宾海板块（NT 1-07）。在前一个位置，棱镜趾处的前缘推力将被穿透，一旦第三阶段钻井与那里的板块边界相交，安装的仪器最终将能够与类似的下倾仪器“通信”。在后一个地点，整个俯冲输入的特点将在现场，这是特别重要的，因为在较低的部分砂是可渗透的，并已被发现与深层流体充电。仪器的开发将与2008年春季安装的美国软木同步进行，该项目已经在进行中。

IODP has started the complex drilling project "NanTroSEIZE" (Nankai Trough Seismogenic Zone Experiment), a multi-stage effort to drill a transect of 7 sites into the the subduction megathrust off Japan. One fundamental goal of NanTroSEIZE is the establishment of a distributed long-term observatory network spanning the incoming plate down to up-dip limit of the seismogenic zone. We here propose installations at two drillsites which are governed by high strains and rapid dewatering in the frontal forearc of the subduction system. At these sites, pore pressure (as a proxy for strain) and temperature will be monitored in sediments of the accretionary wedge and underthrust succession as well as in their equivalent further up-dip. The selected sites are especially critical for monitoring because of their location at the overriding Eurasian Plate (NT 1-03) and the downgoing Phillipine Sea Plate (NT 1-07). In the former location, the frontal thrust at the prism toe will be penetrated, and the installed instruments will be able to eventually "communicate" with similar ones down-dip once Stage 3 drilling intersects the plate boundary there. At the latter site, the entire subduction input will be characterized in situ, which is particularly vital since sands in the lower portion are permeable and have been found charged with deep-seated fluids. Instrument development will be carried out in parallel with an US CORK to be installed in spring 2008, which is already underway.