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

过去20年对俯冲带的观察揭示了板块边界释放应力的一系列模式，包括周期性的慢滑行为。慢滑事件的发生速度介于长期构造板块运动和地震期间的快速滑动速度之间。因此，慢滑被认为跨越了稳定滑动和引发地震的粘滑过程之间的过渡。导致滑移式转换的一个重要机制是流体的聚集和释放所产生的沿断层的压力演化。为了了解新西兰近海Hikurangi边缘的缓慢滑动，有一个协调和广泛的国际采样和监测努力。这项工作中缺失的一部分是在足够长的一段时间内对海底断裂带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型慢滑事件的时间框架内提供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，如科学海洋钻探和旨在了解慢滑事件的地震调查。从科学和社会的角度来看，该项目的成果将有助于我们不仅了解新西兰近海的地震活动，而且了解世界各地的地震活动。这个项目有很大一部分是国际合作的组成部分。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、流体流动和缓慢滑动之间的相互关系，解决了GeoPRISMS计划的俯冲旋回和变形倡议科学计划。在Hikurangi边缘，由于认识到慢滑事件(SSE)的沿走向深度分布及其重复间隔、地震间耦合、推断的孔隙压力和其他与俯冲有关的参数发生了巨大变化，国际上一致努力获取地震学、大地测量学、其他地球物理和地球力学数据。该项目将通过以下方式补充和扩展这些工作：1)在下一次预期的大型SSE的时间范围内，提供两年的流体流动速度和成分的连续记录；2)关于流体流动的当前背景状态及其与推断的沿板块边界的超压的关系的信息；以及3)边缘南北段之间的对比地球化学和水文数据。该工作计划将船舶作业和遥控运载工具(ROV)调查结合在一起，以嵌套方法限制边际范围内的流体流动分布。取心、热流测量和海底流体流量计部署将针对从变形前沿到陆架破裂的断裂带和断层区。断层外的连续流体流量测量将量化滑动过程中流体流动对局部体积应变的响应，断层带的比较数据将提供有关滑动的水文响应的信息。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。

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.