Collaborative Research: Seismic Hazard, Lithosphere Hydration, and Double-Verging Structure of the Puerto Rico Subduction Zone: A Seismic Reflection and Refraction Perspective

波多黎各海沟（PRT）构成重大地震和海啸危险。在这个俯冲带产生的海啸也可能影响美国东海岸。该项目支持PRT和波多黎各的陆地和海洋地震实验。这些实验将确定PRT的详细地震结构，推进我们对PRT的理解，并改善灾害评估。该项目包括：（1）利用海底地震仪绘制的三条广角地震反射/折射剖面图;（2）七条多道地震反射剖面图，其中两条平行于海沟并从海沟向内陆延伸，五条横跨海沟。(3)在波多黎各岛部署了100个短周期陆地节点地震仪阵列。该项目将为培训几名研究生和一名早期职业科学家提供支持，并为少数民族服务机构的教师和学生提供研究机会。该项目支持横跨波多黎各海沟（PRT）、其外部隆起和横跨波多黎各岛弧的有源地震实验。PRT是一个高度倾斜的俯冲带，在这里，古老的大西洋板块以缓慢的速度俯冲到加勒比板块之下。PRT与异常和无法解释的特征有关，例如最宽的海沟（低于6，000米），地球上最低的重力异常，以及波多黎各北海岸的异常沉降。该项目将采集、分析和解释多种类型的数据：三条横跨PRT的广角地震反射/折射剖面，其中一条线延伸到波多黎各岛南部，包括横跨波多黎各岛部署的陆地节点地震仪阵列;七条MCS反射剖面，两条平行于PRT轴，五条垂直于PRT轴;和多波束测深、3.5千赫海底剖面仪、重力和磁力。实验旨在解决三个关键问题：（1）俯冲板片的浅部几何形状及其沿沿着500公里的海沟部分的横向连续性是什么？(2)大西洋岩石圈进入波多黎各海沟的水化程度和空间范围是什么？(3)洋盆两辐逆冲构造系统代表的是双侧俯冲还是单侧俯冲的地壳后楔？综合地震实验，连同其他辅助地球物理数据集，将产生二维地震反射图像、P波和S波走时层析成像二维模型以及研究区域的重力导出密度模型。这些结果有望大大提高我们对上述科学问题的理解和对PRT地震和海啸危险的评估。该奖项反映了NSF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。

The Puerto Rico Trench (PRT) poses major earthquake and tsunami hazards. Tsunamis generated at this subduction zone may also impact the U.S. East Coast. This project supports land and sea seismic experiments across the PRT and Puerto Rico. The experiments will define the detailed seismic structure of the PRT, advance our understanding of the PRT, and improve hazard assessment. The project consists of: (1) Three wide-angle seismic reflection/refraction profiles using ocean bottom seismometers (OBS); (2) Seven multichannel seismic (MCS) reflection profiles, two parallel to and inland from the trench, and five across the trench. (3) An array of 100 short-period land nodal seismometers deployed across the Puerto Rico island. The project will provide support for training several graduate students and an early career scientist, as well as research opportunities for faculty and students at a minority serving institution.This project supports an active-source seismic experiment across the Puerto Rico Trench (PRT), its outer rise, and across the Puerto Rico island arc. The PRT is a highly oblique subduction zone, where old Atlantic plate subducts under the Caribbean plate at a slow rate. The PRT is associated with anomalous and unexplained characteristics, such as the widest trench (below 6,000 m), the lowest gravity anomaly on Earth, and anomalous subsidence of the north coast of Puerto Rico. This project will acquire, analyze, and interpret multiple types of data: Three wide-angle seismic reflection/refraction profiles across the PRT with OBSs, with one of the lines extending to south of the Puerto Rico island and including an array of land nodal seismometers deployed across the Puerto Rico island; seven MCS reflection profiles, two parallel and five perpendicular to the PRT axis; and multibeam bathymetry, 3.5 kHz sub-bottom profiler, gravity, and magnetics. The experiments are designed to address three key questions: (1) What is the shallow geometry of the subducting slab and its lateral continuity along the 500-km section of the trench? (2) What are the degree and spatial extent of hydration of the Atlantic lithosphere entering the Puerto Rico Trench? (3) Does oceanic bivergent thrust system represent double-sided subduction or a crustal retro-wedge of one-sided subduction? The integrated seismic experiments, together with the other ancillary geophysical datasets, will produce two-dimensional seismic reflection images, P-wave and S-wave travel-time tomography 2-D models, and gravity-derived density models of the study region. These results are expected to significantly advance our understanding of the above scientific questions and assessment of the PRT seismic and tsunami hazard.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.