Magnetotelluric Investigation of Subduction Zone Hydrology and Megathrust Slip Behavior at the Nicoya Peninsula

尼科亚半岛俯冲带水文和巨型逆冲滑动行为的大地电磁调查

• 批准号: 2150979
• 负责人: Samer Naif
• 金额: $ 26.36万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-03-01 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2150979&HistoricalAwards=false
• 关键词: Magnetotelluric; Investigation; Subduction; Zone; Hydrology

The west coast of Central America is a convergent plate boundary that regularly experiences large subduction zone earthquakes. In Nicoya Peninsula, Costa Rica, both large damaging earthquakes with significant ground shaking as well aseismic slow-slip events (SSEs) with little to no ground shaking have been observed. Determining why some parts of the plate boundary experience megathrust rupture, while others experience SSEs is important in seismic hazard assessment. It is hypothesized that the style of fault slip may be driven by variations in subsurface fluid content, since fluid-rich zones can lubricate faults while fluid-poor zones promote stick-slip behavior. However, it is unclear precisely what combination of factors dictate the fault slip behavior or whether the hydrology and fluid content are alone responsible. To address these critical unknowns, this project will collect electromagnetic imaging data to constrain the subsurface hydrology and the distribution of fluids beneath the Nicoya Peninsula. The new data will be collected in collaboration with Costa Rican partners at the National University of Costa Rica and the Instituto Costarricense de Electricidad. The data will help distinguish the conditions that enable damaging earthquakes from conditions which promote aseismic slip. This project will support an early-career investigator and a postdoctoral researcher, who will lead the field work and data analysis. Several student volunteers from the U.S. and Costa Rica will be recruited for the fieldwork. Student participants will attend a short-course during the fieldwork where they will: review subduction zone processes and the geology of Nicoya Peninsula specifically, learn about the goals of the project, and receive training to process and analyze the data they helped to collect with freely available open-source software packages. The physical control(s) on the style of fault rupture is fundamental for evaluating seismic hazards, particularly at subduction zones. The Nicoya Peninsula, Costa Rica, is ideal for studying how fluids modulate earthquake behavior due to well-documented variations in seismicity, style of megathrust slip, and plate coupling, in addition to the relatively shallow depth to the plate interface given the survey area’s proximity to the trench. This project will deploy an array of magnetotelluric (MT) instruments at approximately 80 sites to image the three-dimensional electrical resistivity structure beneath the peninsula and constrain the distribution of fluids and thus the geohydrology of the seismogenic zone. The data from this project will be integrated with seismicity and fault slip observations, which are well-resolved by long-term seismic and geodetic instrument networks. The combined data will determine, for example, if electrically conductive regions correlate with zones of SSEs and resistive regions correlate with geodetically-locked zones prone to damaging earthquakes. The MT results will also be combined with geochemical data from surface seeps previously sampled in the survey area in order to determine the sources and migration pathways of fluids emitted at the seeps and how this may impact long term volatile cycling in subduction zone forearcs.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.

中美洲的西海岸是一个收敛的板块边界，经常经历大型俯冲带地地震。在哥斯达黎加的尼科亚半岛，两者都几乎没有观察到几乎没有摇动地面震动的巨大破坏地震，并具有明显的地面摇晃事件（SSE）。确定为什么板边界的某些部分会经历大型破裂，而另一些部分则在地震危险评估中很重要。假设断层滑移的样式可以由地下流体含量的变化驱动，因为富含流体的区域可以润滑断层，而流体贫困区则可以促进粘液滑滑行为。但是，尚不清楚哪种因素的组合决定了断层行为，还是单独的水文和流体含量是造成的。为了解决这些关键的未知数，该项目将收集电子成像数据，以限制尼科亚半岛下面的地下水文学和流体的分布。这些新数据将与哥斯达大学国立大学和哥斯达黎加大学的哥斯达黎加合作伙伴合作收集。数据将有助于区分能够造成损害地震与促进无性滑移的条件的条件。该项目将支持早期研究员和博士后研究人员，他们将领导现场工作和数据分析。来自美国和哥斯达黎加的几名学生志愿者将被招募参加现场工作。学生参与者将在野外工作期间参加短途课程：审查俯冲区流程和尼科亚半岛的地质，特别了解项目的目标，并接受培训以处理和分析他们帮助收集的数据，并提供免费的可用开放源软件包。断层破裂方式的物理控制对于评估地震危害，尤其是俯冲带的基础。哥斯达黎加的尼科亚半岛（Nicoya Peninsula）非常适合研究烟道如何调节地震行为，因为鉴于调查区域靠近沟槽的相对性，除了对板界面的相对浅水深度，除了对板界面界面的相对浅深度外，地震性，巨型滑移风格和板耦合的差异。该项目将在大约80个地点部署一系列磁铁（MT）仪器，以对半岛下方的三维电阻结构进行成像，并限制流体的分布，从而限制地震生成区的地质水文。该项目的数据将与地震性和断层滑移观察结果集成在一起，这些观察结果通过长期地震和地震仪器网络解决。例如，组合数据将确定是否与SSE的区域和抗性区域相关，而耐药区与易于破坏地震的地震区域相关。 MT结果还将与先前在调查区域中取样的地面渗漏的地球化学数据相结合，以确定See散发出的流体的来源和迁移途径，以及这可能会影响长期波动性自行车前期的长期挥发性循环。这是NSF的法律范围和诚实的Intelpriatiach的授权，该奖项已被评估为诚实的依据。