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

在过去的二十年里，对俯冲带的观测揭示了一系列应力释放到板块边界的模式，包括周期性的缓慢滑动行为。缓慢滑动事件的发生速率介于长期构造板块运动和地震期间发生的快速滑动速率之间。因此，缓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压力沿断层沿着的演化是导致滑动方式转变的一个重要机制。国际社会正在进行协调一致的广泛取样和监测工作，以了解新西兰近海希库朗吉边缘的缓慢滑动。这项工作中缺少的一部分是在足够长的时间内沿着沿着海底断层带对流体进行采样和监测，以捕获滑动事件。该项目将解决这一问题，并将在下一个预期的大型缓慢滑动事件的时间范围内提供两年的连续流体流速和成分记录。该项目将为NSF资助的其他正在进行的项目增加价值，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，这个项目的结果将有助于我们了解地震活动不仅在新西兰近海，但在世界各地。这个项目有很大的国际合作成分。该项目支持研究生和本科生的培训。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来解决GeoPRISMS计划的俯冲周期和变形倡议科学计划。在Hikurangi边缘，认识到缓慢滑动事件（SSE）的沿走向深度分布及其复发间隔，地震间耦合，推断孔隙压力和其他俯冲相关参数的巨大变化，导致了国际社会的共同努力，以获取地震，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努力：1）在下一个预期大SSE的时间范围内连续两年记录流体流速和成分; 2）关于流体流动的当前背景状态及其如何与沿沿着板块边界推断的超压相关的信息; 3）边缘北方和南部部分之间的比较地球化学和水文数据。该工作计划结合船舶作业和遥控潜水器（ROV）的调查，在一个嵌套的方法，以限制边缘广泛的流体流量分布。取芯、热流测量和海底流体流量计的部署将针对从变形前沿到陆架断裂的断层带和断层外位置。在断层外连续测量流体流速将量化流体流动对滑移过程中局部体积应变的响应，断层区的比较数据将提供滑移的水文响应信息。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

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.