Hikurangi Trench Regional Electromagnetic Survey to Image the Subduction Thrust

希库朗吉海沟区域电磁勘探对俯冲冲断层进行成像

基本信息

批准号：
1737328
负责人：
Kerry Key
金额：
$ 120.76万
依托单位：
Columbia University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-06-01 至 2023-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1737328&HistoricalAwards=false
关键词：
Hikurangi Trench Regional Electromagnetic Survey

项目摘要

The Hikurangi subduction zone (HSZ) of New Zealand is where the Pacific tectonic plate dives beneath the crust of the North Island along its eastern coast. The HSZ displays marked changes in seismicity and plate-slip along its length: to the south the plates appear to be locked and have the capacity to generate great earthquakes whereas to the north the plates are creeping and regularly host episodic slow slip events and the occasional tsunami earthquake. The physical conditions controlling this contrast in plate coupling is not well understood. Recent investigations suggest fluids may play a critical role. To delineate whether fluids act as a primary control on the style of slip expressed along the HSZ, this study will use electromagnetic (EM) methods to image the electrical resistivity structure of the HSZ. Our measurements will provide important constraints on the hydrologic architecture by quantifying the along and across-strike variations in porosity and the fluid budget of the HSZ. This project will support a Ph.D. student and several graduate students, postdocs and early career scientists will be involved in the field work. The PI is an early career scientist who will gain valuable experience leading the field project and mentoring a graduate student. Additionally, a marine EM short-course will be given for students and unfunded collaborators to learn about marine EM theory, applications, data processing, and inverse modeling.This project will use newly proven marine EM imaging technology to constrain the porosity and fluid budget of the crust and mantle along both segments of the HSZ. The survey cruise will deploy a grid of ocean-bottom EM receivers in a 400 km by 150 km area that spans the incoming plate and fore-arc margin. Magnetotelluric (MT) response functions will be estimated from the recorded electric and magnetic field time-series. In addition, controlled-source EM (CSEM) data will be recorded by deep towing a horizontal electric dipole transmitter near the seafloor along three trench-crossing transects located in the southern, central, and northern segments of the HSZ. The MT and CSEM data will be inverted for electrical resistivity and used to quantify the porosity structure across the margin. The HSZ resistivity results will be interpreted in conjunction with existing and planned geophysical and drilling data to test the hypothesis that along-strike variations in seismicity and interplate locking are related to the fluid budget of the incoming oceanic plate, fluid content along the plate interface, and upper plate permeability/porosity structure. The MT data will also image the electrical resistivity of the lithosphere and asthenosphere, providing independent constraints on the origin of the lithosphere-asthenosphere boundary.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.

新西兰的希库朗伊俯冲带（HSZ）是太平洋板块沿其东海岸潜入北岛地壳之下的地方。 HSZ 沿其长度显示出地震活动和板块滑移的显着变化：在南部，板块似乎被锁定并有能力产生大地震，而在北部，板块正在蠕动，经常发生偶发性慢滑事件和偶尔发生的板块滑移事件。海啸地震。控制板耦合中这种对比度的物理条件尚不清楚。最近的研究表明液体可能发挥着关键作用。为了描述流体是否对沿着 HSZ 表达的滑移类型起到主要控制作用，本研究将使用电磁 (EM) 方法对 HSZ 的电阻率结构进行成像。我们的测量将通过量化沿线和跨走向的孔隙度变化以及 HSZ 的流体预算，为水文结构提供重要的约束。该项目将支持博士学位。学生和几名研究生、博士后和早期职业科学家将参与实地工作。 PI 是一位早期职业科学家，他将获得领导该领域项目和指导研究生的宝贵经验。此外，将为学生和无资助的合作者提供海洋电磁短期课程，以了解海洋电磁理论、应用、数据处理和反演建模。该项目将使用新近经过验证的海洋电磁成像技术来限制海洋电磁场的孔隙度和流体预算。沿 HSZ 两段的地壳和地幔。勘测巡航将在 400 公里 x 150 公里的区域内部署海底电磁接收器网格，跨越传入板块和弧前边缘。大地电磁 (MT) 响应函数将根据记录的电场和磁场时间序列进行估计。此外，将通过沿着位于 HSZ 南段、中段和北段的三个跨海沟横断面在海底附近深拖水平电偶极子发射机来记录受控源电磁 (CSEM) 数据。 MT 和 CSEM 数据将进行电阻率反演，并用于量化边缘的孔隙结构。 HSZ 电阻率结果将结合现有和计划的地球物理和钻井数据进行解释，以检验以下假设：地震活动的沿走向变化和板间锁定与传入海洋板块的流体预算、沿板块界面的流体含量、和上板渗透率/孔隙率结构。 MT 数据还将对岩石圈和软流圈的电阻率进行成像，为岩石圈-软流圈边界的起源提供独立的约束。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的评估进行评估，被认为值得支持。影响审查标准。