Collaborative Research: Slow-Slip and Fluid Flow Response Offshore New Zealand -Probing The Nature Of The Margin Hydrogeochemical System

过去二十年来对俯冲带的观测揭示了在板块边界上应力释放的一系列模式，包括周期性慢滑行为。缓慢滑动事件发生的速度介于长期构造板块运动和地震期间发生的快速滑动速度之间。因此，慢滑动被认为跨越了稳定滑动和产生地震的粘滑过程之间的过渡。流体的聚集和释放所产生的沿断层的压力演化是导致滑型转变的一个重要机制。为了了解新西兰近海Hikurangi边缘的缓慢滑动，国际上进行了协调一致的广泛采样和监测工作。这项工作中缺少的一项工作是在足够长的时间内对海底断裂带沿线的流体进行采样和监测，以捕捉滑动事件。该项目将解决这一问题，并将在下一次预期的大慢滑事件的时间框架内提供为期两年的流体流速和成分的连续记录。该项目将为其他正在进行的nsf资助的项目增加价值，例如旨在了解慢滑事件的科学海洋钻探和地震调查。从科学和社会的角度来看，这个项目的结果不仅有助于我们了解新西兰近海的地震活动，而且有助于我们了解全世界的地震活动。这个项目有很大一部分是国际合作。该项目支持研究生和本科生的培养。该项目通过测试新西兰Hikurangi边缘的流体生产、流体流动和慢滑之间的相互关系，解决了GeoPRISMS计划的俯冲旋回和变形主动科学计划。在Hikurangi边缘，由于认识到慢滑事件（sse）沿走向深度分布的剧烈变化及其重复间隔、地震间耦合、推断孔隙压力和其他与俯冲有关的参数，国际上共同努力获取地震、大地测量、其他地球物理和地质力学数据。该项目将通过以下方式补充和扩展这些工作：1)在下一个预期的大型SSE的时间框架内，提供为期两年的流体流速和成分的连续记录；2)流体流动的当前背景状态及其与沿板块边界推断的超压的关系；3)对比南北段边缘的地球化学和水文资料。该工作计划将船舶作业和远程操作车辆（ROV）测量结合在一起，以嵌套的方式约束边缘流体流动分布。取心、热流测量和底栖流体流量计的部署将针对断层带和非断层位置，从变形前沿到大陆架断裂。在非断层位置连续的流体流速测量将量化滑动期间流体对局部体积应变的响应，而在断裂带的比较数据将提供关于滑动的水文响应的信息。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Observations at subduction zones over the past two decades have revealed a range of modes by which stress is released on the plate boundary, including periodic slow slip behavior. Slow slip events occur at a rate intermediate between long-term tectonic plate motion and the fast slip velocity that occurs during earthquakes. Thus, slow slip is thought to span the transition between stable slip and the stick-slip process that generates earthquakes. An important mechanism that could cause the transitions in slip style is the evolution of pressure along the fault that is generated by the accumulation and release of fluids. There is a concerted and extensive international sampling and monitoring effort to understand slow slip at the Hikurangi margin offshore New Zealand. A missing piece in this effort is the sampling and monitoring of fluids along seafloor fault zones over a long enough period of time to capture a slip event. This project will address this problem and will provide a two-year continuous record of fluid flow rate and composition over the time frame of the next expected large slow slip event. The project will add value to other ongoing NSF-funded programs at this margin such as scientific ocean drilling and seismic surveys aimed at understanding slow slip events. From both the scientific and societal perspectives, results from this project will contribute to our understanding of earthquake activity not only offshore New Zealand but worldwide. This project has a large component of international collaboration. The project supports the training of graduate and undergraduate students. This project addresses the GeoPRISMS Program's Subduction Cycles and Deformation Initiative Science Plan by testing interrelationships between fluid production, fluid flow, and slow slip at the Hikurangi margin off New Zealand. At the Hikurangi margin, the recognition of dramatic changes in the along-strike depth distributions of slow-slip events (SSEs) and their recurrence intervals, interseismic coupling, inferred pore pressure, and other subduction-related parameters have resulted in a concerted international effort to acquire seismological, geodetic, other geophysical, and geomechanical data. This project will complement and extend these efforts by providing 1) a two-year continuous record of fluid flow rate and composition over the timeframe of the next expected large SSE; 2) information on the present background state of fluid flow and how it relates to inferred overpressure along the plate boundary; and 3) comparative geochemical and hydrologic data between the northern and southern sections of the margin. The work plan combines ship operations and Remotely Operated Vehicle (ROV) surveys in a nested approach to constrain the margin-wide fluid flow distribution. Coring, heat flow measurements, and benthic fluid flow meter deployments will target fault zones and off-fault locations from the deformation front to the shelf-break. Continuous fluid flow rate measurements at off-fault locations will quantify the fluid flow response to local volumetric strain during slip, and comparative data at fault zones will provide information on the hydrologic responses to slip.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.