Installation of a Seafloor Geodesy Observatory in the Northern Chille Subduction Zone

在过去的十年里，发生了许多8-9级俯冲带大规模地震，其中一些产生了非常具有破坏性的海啸。在这种事件中，大多数断层滑动发生在覆盖板块大陆架下的近海。在这些大地震之前的知识状态的局限性，以及他们的破裂过程的文件，是缺乏海上地震和大地测量仪器以上的断层破裂带的直接结果。这项研究增加了一项国际努力，将开始在纳斯卡-南美洲板块边界的伊基克段安装海底仪器，预计将发生强烈到破坏性（Mw 8.5）的地震。现在安装仪器将允许在导致大地震的地震周期的终端阶段监测变形。该地区的独特之处在于，其预测的大地震发生的可能性似乎是有根据的。最近在研究区域北部发生的8.1级地震表明，大地耦合模型是正确的，纳斯卡-南美洲板块边界的这一部分已经被锁定，并积累了相当大的应变，将继续释放地震。一些机械和水文特性控制着一个给定的大型俯冲地震是否会在海沟附近发生高危险性的浅层滑动。在短期研究中可以量化的一个因素是海沟附近弧前的持续变形，这可以通过数值模型与底层断层的锁定（相对于缓慢的抗震滑动）状态相关。将通过智利-德国-美国合作在伊基克段安装的陆上/海上地震和大地测量观测台有可能成为第一个8级地震的震间-同震-震后数据集，仪器从海沟一直延伸到锁定区。研究的美国部分将在3年内沿弧前斜坡15公里的横断面部署9个海底声学测距仪器沿着。将根据新的自主式潜水器海底测绘确定站点位置，并将其嵌套在为主要研究部署的约100公里陆架-海沟断面内。每个小组的不同声学仪器的托管提供了交叉校准不同技术的重要机会，这有助于将海底大地测量从过去的验证阶段转变为一门强大的科学。培训一名研究生获取和处理大地测量数据将增加这一发展中研究领域的劳动力。

The last ten years has seen many magnitude 8-9 subduction zone megathrust earthquakes, several of which generated remarkably destructive tsunami. A majority of fault slip during such events occurs offshore underneath the continental shelf of the overriding plate. Limitations in the state of knowledge before these great earthquakes, and documentation of their rupture process, is a direct result of the lack of offshore seismic and geodetic instrumentation above the fault rupture zones. This study adds to an international effort that will initiate installation of seafloor instrumentation on the Iquique segment of the Nazca-South American plate boundary, on which a strong to devastating (Mw 8.5) earthquake is expected to occur. Installing instrumentation now will allow monitoring of deformation in the terminal stage of a seismic cycle leading up to a great earthquake. The region is unique in that predicted likelihood of its readiness for a major quake appears to be well-founded.A recent M8.1 earthquake just to the north of the study area demonstrates that geodetic coupling models were correct that this segment of the Nazca-South America plate boundary has been locked and built up considerable strain that will continue to be released seismically. A number of mechanical and hydrological properties control whether a given large subduction earthquake will involve high-hazard, shallow slip near the trench or not. One factor that can be quantified in a short-term study is the ongoing deformation of the forearc near the trench, which can be related through numerical models to the locking (versus slowly, aseismically slipping) status of the underlying fault. The onshore/offshore seismic and geodetic observatory to be installed in the Iquique segment through a Chilean-German-US collaboration has potential to be the first interseismic-coseismic-post-seismic dataset for a M8 earthquake with instrumentation spanning all the way from the trench through the locked zone. The US component of the study will deploy 9 seafloor acoustic ranging instruments along a 15 km transect across the forearc slope for 3 years. Stations will be sited on the basis of new AUV seafloor mapping and will be nested within a ~100 km shelf-trench transect deployed for the main study. The colocation of each group's different acoustic instruments provides an important opportunity to cross calibrate different technology, which can help transition seafloor geodesy out of the past proofing stage into a robust science. Training of a graduate student in acquisition and processing of the geodetic data will increase the workforce in this developing research area.