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级俯冲带大地震，其中几次引发了极具破坏性的海啸。在这类事件中，大多数断层滑动发生在逆冲板块的大陆架下的近海。在这些大地震之前的知识状态以及对其破裂过程的记录的局限性，是缺乏断层破裂带上方的近海地震和大地测量仪器的直接结果。这项研究是一项国际努力的补充，它将启动在纳斯卡-南美板块边界的伊基克段安装海底仪器的工作，预计在那里将发生一场强烈到毁灭性(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末期阶段监测变形。该地区的独特之处在于，其为大地震做好准备的预测可能性似乎是有充分依据的。最近发生在研究区北部的8.1级地震表明，大地测量耦合模型是正确的，即这段纳斯卡-南美板块边界已经锁定，并建立了相当大的应变，将继续通过地震释放。许多力学和水文特性控制着给定的大俯冲地震是否会涉及海沟附近的高风险、浅层滑动。在短期研究中可以量化的一个因素是海沟附近的前弧的持续变形，这可以通过数值模型与下伏断层的锁定状态(而不是缓慢的无震滑动)联系起来。将通过智利-德国-美国的合作安装在伊基克段的陆上/近海地震和大地测量观测站有可能成为第一个8级地震的震间-同震-震后数据集，其仪器设备从海沟一直跨越到锁定区。这项研究的美国部分将在横跨弧前斜坡的15公里横断面上部署9台海底声波测距仪器，为期3年。空间站将在新的AUV海底测绘的基础上选址，并将嵌套在为主要研究部署的约100公里陆架沟横断面内。每组不同声学仪器的共同定位提供了交叉校准不同技术的重要机会，这可以帮助海底大地测量走出过去的验证阶段，成为一门强大的科学。对一名研究生进行获取和处理大地测量数据的培训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.