Collaborative Research: Along Strike Variation in Shallow, Offshore Strain Accumulation and Slow Slip at Hikurangi Subduction Margin, New Zealand

俯冲带是指地球上的一个板块滑到另一个板块之下的区域。两个板块之间的滑移区是一个地质断层，在那里，下部板块的运动通过摩擦过程不完全地传递到上覆板块，从而允许未释放的应变在上部板块中积累。上板块积聚应变的突然释放引发了地震，由于滑移区的大小，俯冲带上的地震可能会很大。这些大地震不仅造成了地震本身的破坏，也造成了海啸造成的海水泛滥。最近在2004年苏门答腊岛、2010年智利和2011年日本发生的事件都表明了与这些事件相关的毁灭性危险。俯冲区还位于加利福尼亚州北部、俄勒冈州和华盛顿州以及阿拉斯加和阿留申群岛沿岸的美国海岸附近。这两个俯冲带过去都经历过大地震，未来还会再次经历。该项目的一个目标是更好地了解俯冲带的地球物理过程，并改进对潜在危险的定量评估。该项目将部署海底大地测量传感器的组合，以跟踪新西兰俯冲区近海海底运动的缓慢积累和可能的释放。之所以选择新西兰Hikurangi遗址，是因为俯冲带很浅，使用海底大地测量仪器可以更有效地进行成像。该遗址还拥有快速重复的慢滑地震的历史，为了解滑动过程提供了洞察。该项目的更广泛影响包括对研究中的研究生的培训和支持。该项目利用了新西兰和日本研究小组的国际努力，他们将占据邻近的海底大地测量地点。该项目还将向新西兰研究同行转让如何进行海底大地测量实验的业务知识，使他们能够在这一拟议项目期间收集这些关键地点的测量结果，并在项目结束后的未来继续进行。该项目将使用全球定位系统声学(GPS-A)方法在四年期间测量新西兰Hikuangi俯冲边缘海沟附近的形变。GPS-A站点将建立在霍克斯湾地区，以利用日本和新西兰的资金建立的边缘地区北部和南部的GPS-A站点之间的关键测量为中心。这个中心地点接近从明显强烈耦合的边缘到南部的过渡，而在北部则是几乎不耦合的边缘。该项目将为GPS声学测量实施更高效、更节约成本的Wave Glider平台。将安装用于水平定位的永久性海底基准，以确保该位置的时间序列可以延续到本项目结束后的未来。一系列绝对压力计也将部署两年，以测量从霍克斯湾地区下方的陆地阵列观察到的缓慢滑动事件的离岸程度，根据古地震学，该地区过去被认为经历了多次8级地震。该阵列预计将在部署期间探测到垂直隆起，从而探测到该地区至少一个大型慢滑事件的空间范围。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Subduction zones are regions where one of Earth's tectonic plates slides beneath another. The zone of slip between the two plates is a geologic fault where the motion of the lower plate is imperfectly transferred to the overlying plate through frictional processes allowing for unreleased strain to build up in the upper plate. The abrupt release of built-up strain in the upper plate causes earthquakes, which can be large on subduction zones because of the size of the slip region. These great earthquakes cause damage both from the shaking itself but also because of the flooding of seawater from a tsunami. Recent events in Sumatra in 2004, Chile in 2010, and Japan in 2011 all demonstrate the devastating hazard associated with these events. Subduction zones also lie offshore the US coasts along Northern California, Oregon and Washington State and another along Alaska and the Aleutian Islands. Both of these subduction zones have experienced great earthquakes in the past and will do so again in the future. A goal of this project is to better understand the geophysical processes at work at subduction zones and to improve the quantitative assessment of potential hazard. This project will deploy a combination of seafloor geodetic sensors to track the slow buildup and possible release of seafloor motion offshore of a New Zealand subduction zone. The New Zealand Hikurangi site was picked because the subduction zone is shallow and can be imaged more effectively with seafloor geodetic instruments. This site also has a history of rapidly repeating slow slip earthquakes that provide insight into the slip process. Broader impacts of this project include training and support for a graduate student in the research. The project leverages international efforts by New Zealand and Japanese research teams who will occupy adjacent seafloor geodetic sites. The project will also transfer operational know-how for how to conduct seafloor geodesy experiments to NZ research counterparts, enabling them to collect measurements at these critical sites during this proposed project and continue in the future past the end of the project.This project will measure deformation near the trench of the New Zealand Hikuangi subduction margin over a four year period using the GPS-Acoustic (GPS-A) method. The GPS-A site will be established in the Hawkes Bay area to provide critical measurements centered between GPS-A sites in the northern and southern parts of the margin established using Japanese and New Zealand funding. This central site is near the transition from an apparently strongly coupled margin to the South, and a nearly uncoupled margin in the North. The project will implement the more efficient and cost-saving Wave Glider platform for the GPS-Acoustic measurements. Permanent seafloor benchmarks will be installed for horizontal positioning to ensure the time series of positions can be continued into the future, past the end of this project. An array of absolute pressure gauges will also be deployed for two years to measure the offshore extent of slow slip events observed from land arrays beneath the Hawkes Bay area, a region thought to have experienced many 8 magnitude earthquakes in the past based on paleoseismology. The array is expected to detect vertical uplift and hence the spatial extent of at least one large slow slip event in this region during the deployment.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.