MeBoCORK: Development of borehole observatories for MeBo (MARUM Meeresboden- Bohrgerät): Application to the seismogenic Nankai Trough subduction zone, Japan

地球上大约90%的地震力矩是在毁灭性的俯冲带地震中释放的。在综合海洋钻探计划（lODP）中，沿活动辐合边缘的孕震研究在名为“NanTroSEIZE”（南开槽孕震带实验）的多科考活动中起着关键作用。迄今为止，8个考察队（lODP考察队314-316、319、322、326、332-333）沿着一条横断面钻探了12个地点，从进入的板块穿过正面增生棱镜到弧前盆地。在不久的将来，最深的井将使用立管钻井进入俯冲大逆冲的发震部分。他参加了NanTroSEIZE的三次探险，最近一次是作为联合首席科学家监督迷你软木塞的成功回收以及迷你软木塞和完整软木塞天文台的安装（Exp 332）。该提案旨在达到两个主要的科学里程碑：(i)除了lODP钻孔观测网的德国部分（即319和332期间的迷你软木塞以及对整个软木塞的一些贡献），我们希望将长期监测工作扩展到C0009站点向陆地约30公里处的活火山。这些特征携带着天然气水合物和深层流体，最有可能进入海底以下几公里深处的发震带，并且也覆盖在高应变和锁定板块边界的区域上。（ii）第二个目标是开发一个智能MeBo （MARUM Meeresboden-Bohrgerät）科克天文台，安装在其中两座泥火山上。这些观测站将是独立的，监测孔隙压力和温度，作为钻孔末端深度附近应变和流体流动的代表。其液压管线可进一步用于地球化学（渗透采样器）和微生物（絮凝装置）监测和采样。在新的lODP科学计划中，MeBo等专业平台被讨论为ECORD在2013-2023年的贡献。到目前为止，CORKs或其他复杂的长期设备仅限于DVs Joides Resolution和Chikyu，然而，我们在这里为多功能，多学科的MeBo井眼仪器提供了一种经济实惠的解决方案。拟议的系统将由MeBo单独安装，数据可以由机会船检索。通过rov（在预期的lODP考察期间和/或之后）部署和回收的海底延伸部分可以增加能力和有效载荷，因此代表了超过十年的监测手段。数据恢复将来自机遇之船，因此经常是可能的。南开泥火山油田的MeBo钻井和ROV装置的资金已经获得批准（RV Sonne巡航SO222于2012年夏季），并作为实物贡献纳入该项目。

Approximately 90% of the seismic moment on Earth is released in often devastating subduction zone earthquakes (EQs). In the Integrated Ocean Drilling Program (lODP), the study of seismogenesis along an active convergent margin plays a key role in the form of a multi-expedition effort named "NanTroSEIZE" (Nankai Trough Seismogenic Zone Experiment). To date, eight expeditions (lODP Expeditions 314-316, 319, 322, 326, 332-333) drilled 12 sites along a transect from the incoming plate across the frontal accretionary prism to the forearc basin. In the near future, the deepest hole will tap into the seismogenic portion of the subduction megathrust using Riser drilling. The proponent participated in three of the NanTroSEIZE expeditions, most recently as co-chief scientist overseeing the successful recovery of a mini-CORK and the installation of a mini-CORK and a full CORK observatory (Exp 332). This proposal aims lo reach two major scientific milestones:(i) In addition to the German component of the lODP borehole observatory network (i.e. mini- CORKs during Legs 319 and 332 plus some contribution to the full CORK), we want to extend the long-term monitoring efforts to active mud volcanoes some 30 km landward of Site C0009. These features carry gas hydrates and deep-seated fluids, most likely tapping into the seismogenic zone at a depth of several km below seafloor, and are also overlying an area of high strains and a locked plate boundary-thrust.(ii) The second goal is to develop a smart MeBo (MARUM Meeresboden-Bohrgerät) CORK observatory to be installed in two of these mud volcanoes. These observatories will be self-contained and monitor pore pressure and temperature as proxies for strain and fluid flow near terminal depth of the borehole. Their hydraulic lines can further be used for geochemical (osmo-sampler) and microbiological (FLOCS units) monitoring and sampling.The underlying reason for the engineering effon of smart observatories for MeBo is founded in the new lODP Science Plan where specialist rigs such as MeBo are discussed as ECORD's contribution from 2013-2023. So far, CORKs or other sophisticated long-term devices were restricted to DVs Joides Resolution and Chikyu, however, we here present an affordable solution for versatile, multi-disciplinary MeBo borehole instruments. The proposed system is to be installed by MeBo alone and data can be retrieved by ships of opportunity. A seafloor extension, to be deployed and recovered by ROVs (during and/or after the anticipated lODP expedition) can add capability and payload, and hence represent the means for more than decade of monitoring. Data recovery will be from ships of opportunity and hence frequently possible.Funding for MeBo drilling and ROV installations in the Nankai mud volcano field has already been granted (RV Sonne cruise SO222 in summer 2012) and is brought into the project as in kind contribution.