Collaborative Research: Seismic Investigation of the Puerto Rico Subduction Zone: Structure, Seismic Hazard, and Hydration of Slow-spreading Lithosphere

波多黎各俯冲区的地震调查波多黎各海沟(PRT)构成了重大的地震和海啸危险。在这个俯冲带产生的海啸也可能影响美国东海岸。该项目支持整个PRT和波多黎各的陆地和海洋地震试验。这些实验将确定PRT的详细地震结构，增进我们对PRT的理解，并改进危险评估。该项目包括：(1)使用海底地震仪(OBS)的三条广角地震反射/折射剖面；(2)四条多道地震(MCS)反射剖面，其中两条平行于海沟，两条平行于中央海底地震仪(OBS)。(3)部署在波多黎各全岛的100多台短周期陆地地震仪阵列，以及记录地震18个月的十几台宽带地震仪。该项目将为培养几名研究生和一名早期职业科学家提供支持，并为少数族裔服务机构的教职员工和学生提供研究机会。该项目还将支持对科学记者的培训和对波多黎各居民的公开演讲。该项目支持一项横跨波多黎各海沟(PRT)、其外隆起和横跨岛弧的有源地震实验，以及一项陆地被动震源实验。PRT是一个高度倾斜的俯冲带，在那里旧的大西洋板块以缓慢的速度俯冲到加勒比海板块之下。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下沉。该项目将获取、分析和解释多种类型的数据：在波多黎各群岛南部使用OBSS和一条附加线横跨PRT的三条广角地震反射/折射剖面；四条MCS反射剖面，每个剖面两条平行于和垂直于PRT轴；波多黎各岛上一个有源和无源陆地地震台阵列；以及多波束水深测量，3.5千赫次海底剖面仪、重磁。这些实验旨在解决三个关键问题：(1)俯冲板块的浅几何形状及其沿500公里海沟的横向连续性是什么？(2)进入波多黎各海沟的大西洋岩石圈的水化程度和空间范围是什么？(3)大洋两分向逆冲系统代表的是双面俯冲还是地壳单面俯冲的后楔形？综合地震实验的结果预计将显著促进我们对上述科学问题的理解以及对PRT地震和海啸危险的评估。这一奖项反映了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。

Seismic investigation of the Puerto Rico subduction zoneThe 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) Four multichannel seismic (MCS) reflection profiles, two parallel to and inland from the trench, and two parallel to the central OBS profile. (3) An array of more than 100 short-period land seismometers deployed across the Puerto Rico island, together with a dozen broad-band seismometers to record earthquakes for 18 months. 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. The project will also support training of science journalists and public lectures to reach Puerto Rico residents.This project supports an active-source seismic experiment across the Puerto Rico Trench (PRT), its outer rise, and across the island arc, together with a land passive-source experiment. 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 and an additional line south of the Puerto Rico island; four MCS reflection profiles, two each parallel and perpendicular to the PRT axis; an array of active- and passive-source land seismic stations on the Puerto Rico island; 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? Results of the integrated seismic experiments 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.