Three Dimensional Seismic Velocity Structure of Puerto Rico Virgin Island Microplate

波多黎各维尔京群岛微板三维地震速度结构

• 批准号: 1722991
• 负责人: Elizabeth Vanacore
• 金额: $ 9.51万
• 依托单位: University of Puerto Rico Mayaguez
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1722991&HistoricalAwards=false
• 关键词: Three; Dimensional; Seismic; Velocity; Structure

This project aims to study the structure and tectonics of the Puerto-Rico and Virgin Islands region located at the northeastern border of the Caribbean Plate. In this region, the North American plate is subducting beneath the Caribbean Plate. This interaction between the North American and Caribbean Plates results in significant earthquake activity including the 1918 earthquake and tsunami that devastated western coast of Puerto Rico. Currently, there are multiple tectonic models proposed to describe the interaction between the two plates. However, these models are currently poorly constrained by the available analyzed datasets. The primary goal of this project is to generate high quality seismic velocity images and refined earthquake location data that will provide data based constraints for the regional scientific models and enhance knowledge of the regional earthquake and tsunami hazard. This scientific study will involve two major processes, a relocation of the Puerto Rico Seismic Network earthquake catalog for the years 2015-2017 and a three-dimensional seismic velocity imaging of the region. This time period has been specifically selected to create a synergetic dataset with a current seismic experiment in the Dominican Republic (eastern Hispaniola). The direct data tie between this project and the project in Hispaniola will permit the future combination of the two separate datasets, the creation unified products, and promote scientific partnerships in the region. The first methodology to be applied in this study, earthquake relocation, is the process in which the earthquake locations determined by regional seismic networks and the United States Geological Survey (USGS), which are real-time fast solutions designed to provide information to emergency agencies, are re-examined in detail and refined using more advanced but time consuming computer algorithms as well as additional data that was not available in real-time to generate more accurate locations. The second methodology of this study, travel time tomography, is a method in which a three-dimensional seismic velocity image of the Puerto Rico-Virgin Islands region will be produced in a procedure analogous to how the human body is imaged in a medical CT scan. The imaging to be performed in this study will reveal the regional structure of the Earth's crust and upper mantle. This image combined with the relocated earthquake catalog will provide a robust view of the active tectonic processes that drive the observed regional seismic activity and provide data constraints for future scientific tectonic models. The products generated by this investigation, the relocated earthquake location catalog and seismic velocity imaging, will not only enhance scientific knowledge but also enhance the knowledge of the local earthquake and tsunami hazard. The relocation of local events will permit the identification of the most active faults within the Puerto Rico and Virgin Islands region, especially in Great Southern Puerto Rico Fault Zone and Great Northern Puerto Rico Fault Zone. Consequently, this will aid in the process of updating the Puerto Rico seismic hazard map which has not been revised by the USGS since 2003. The three-dimensional seismic velocity model will be used to determine if the current Puerto Rico Seismic Network one-dimensional velocity model used for earthquake location requires an update. The results of this study will be presented to the general public as short articles in the University of Puerto Rico Mayagüez website and Puerto Rico Seismic Network outreach materials, which impacts hundreds of school children and teachers throughout Puerto Rico every year. This research will also enhance participation of underrepresented students and faculty in the geosciences. The master's student at University of Puerto Rico Mayagüez (a Hispanic Serving Institution) will be funded to conduct the research as part of his/her thesis. The student and principal investigator will also present their research in national meetings and publish in peer-reviewed journals. This study proposes to focus on the seismic structure of the Puerto Rico-Virgin Islands Microplate (PRVIM), one of several proposed microplates in the deformation zone of the northeastern Caribbean margin. Of particular interest is the structure and dynamics of the subducting North American Plate beneath the PRVIM. Multiple tectonic models have been proposed for the dynamics across Hispaniola and the PRVIM. However, these models are currently poorly constrained by the available analyzed datasets. The primary goal of this project is to generate high quality seismic velocity images and refined earthquake location data that will provide data based constraints for the regional scientific models and enhance knowledge of the regional earthquake and tsunami hazard. This scientific study will involve two major processes, a relocation of the Puerto Rico Seismic Network earthquake catalog for the years 2015-2017 and a three-dimensional seismic tomography. This time period has been specifically selected to create a synergetic dataset with a current seismic experiment in the Dominican Republic (eastern Hispaniola). The direct data tie between this project and the project in Hispaniola will permit the future combination of the two separate datasets, the creation unified products, and promote scientific partnerships in the region. This project will generate a relocated event catalog dataset to sharpen the structures that are imaged on the PRVIM via seismicity including the Great Northern Puerto Rico Fault Zone, the subducted North American plate, and possible slab tears in the Mona Passage and Sombrero Seismic Zone. Additionally, a three-dimensional tomography using the FMTOMO program will be performed to image the detailed seismic velocity structure and aid in the identification/corroboration of significant seismic features related to the oblique subduction system. The detailed seismic imaging of this relatively understudied subduction zone will provide insight into the slab structure and dynamics of this oblique margin. The earthquake relocation and tomographic imaging aim to provide a high-resolution picture of the subducting slab structure beneath the PRVIM as well as determine if the two earthquake swarm locations denote slab tears similar to what has been imaged on the south side of the Caribbean Plate by the BOLIVAR project. The high-resolution imaging will also provide seismic constraints for future geodynamic models. In addition to increasing the understanding of the dynamics of oblique subduction zone, the products of this proposal will permit the identification of the most active faults within the PRVIM, especially in Great Southern Puerto Rico Fault Zone and Great Northern Puerto Rico Fault Zone. Consequently, this will aid in the process of updating the Puerto Rico seismic hazard map which has not been revised by the USGS since 2003. The updated three-dimensional seismic velocity model will be used to determine if the current Puerto Rico Seismic Network one-dimensional velocity model used for earthquake requires an update. The results of this study will be presented to the general public as short articles in the University of Puerto Rico Mayagüez website and Puerto Rico Seismic Network outreach materials, which impacts hundreds of school children and teachers throughout Puerto Rico every year. This research will also enhance participation of underrepresented students and faculty in the geosciences. The master's student at University of Puerto Rico Mayagüez (a Hispanic Serving Institution) will be funded to conduct the research as part of his/her thesis. The student and primary investigator will also present their research in national meetings and publish in peer-reviewed journals.

该项目旨在研究位于加勒比海板块东北边界的波多黎各和维尔京群岛地区的结构和构造。在这个地区，北美板块俯冲到加勒比板块之下。北美板块和加勒比板块之间的这种相互作用导致了重大的地震活动，包括1918年摧毁波多黎各西海岸的地震和海啸。目前，人们提出了多种构造模型来描述两个板块之间的相互作用。然而，这些模型目前很少受到可用分析数据集的约束。该项目的主要目标是生成高质量的地震速度图像和精确的地震位置数据，这些数据将为区域科学模型提供基于数据的约束，并增强对区域地震和海啸危害的认识。这项科学研究将涉及两个主要过程，一是重新定位波多黎各地震台网2015-2017年地震目录，二是对该地区进行三维地震速度成像。在多米尼加共和国（伊斯帕尼奥拉岛东部）的当前地震实验中，特别选择了这个时间段来创建一个协同数据集。该项目与伊斯帕尼奥拉岛项目之间的直接数据联系将允许未来将两个独立的数据集结合起来，创建统一的产品，并促进该地区的科学伙伴关系。本研究中应用的第一种方法是地震重新定位，这是一个过程，其中由区域地震台网和美国地质调查局（USGS）确定的地震位置是旨在向紧急机构提供信息的实时快速解决方案，使用更先进但耗时的计算机算法以及无法实时获得的其他数据重新详细检查和改进，以产生更准确的位置。本研究的第二种方法，旅行时间断层扫描，是一种产生波多黎各-维尔京群岛地区三维地震速度图像的方法，其过程类似于医学CT扫描中人体成像的方式。在这项研究中进行的成像将揭示地壳和上地幔的区域结构。该图像与重新定位的地震目录相结合，将为驱动观测到的区域地震活动的活动构造过程提供一个强有力的视图，并为未来的科学构造模型提供数据约束。这次调查产生的产品，即重新定位的地震位置目录和地震速度成像，不仅可以增强科学知识，还可以增强对当地地震和海啸危害的认识。对当地事件的重新定位将允许识别波多黎各和维尔京群岛地区最活跃的断层，特别是在大南波多黎各断裂带和大北波多黎各断裂带。因此，这将有助于更新波多黎各地震危险图的过程，该地图自2003年以来一直没有被美国地质调查局修订过。三维地震速度模型将用于确定当前用于地震定位的波多黎各地震台网一维速度模型是否需要更新。这项研究的结果将以短文形式在波多黎各大学mayagez网站和波多黎各地震网络推广材料中向公众展示，每年影响波多黎各各地数百名学生和教师。这项研究还将加强未被充分代表的学生和教师在地球科学领域的参与。波多黎各大学mayagez（西班牙裔服务机构）的硕士生将获得资助，作为他/她论文的一部分进行研究。学生和首席研究员还将在国家会议上展示他们的研究成果，并在同行评议的期刊上发表。本研究拟重点研究波多黎各-维尔京群岛微板块（PRVIM）的地震结构，该微板块是加勒比海东北部边缘形变带的几个被提出的微板块之一。特别令人感兴趣的是在PRVIM之下俯冲的北美板块的结构和动力学。对于伊斯帕尼奥拉岛和PRVIM的动力学，提出了多种构造模型。然而，这些模型目前很少受到可用分析数据集的约束。该项目的主要目标是生成高质量的地震速度图像和精确的地震位置数据，这些数据将为区域科学模型提供基于数据的约束，并增强对区域地震和海啸危害的认识。这项科学研究将涉及两个主要过程，2015-2017年波多黎各地震台网地震目录的重新定位和三维地震层析成像。在多米尼加共和国（伊斯帕尼奥拉岛东部）的当前地震实验中，特别选择了这个时间段来创建一个协同数据集。该项目与伊斯帕尼奥拉岛项目之间的直接数据联系将允许未来将两个独立的数据集结合起来，创建统一的产品，并促进该地区的科学伙伴关系。该项目将生成一个重新定位的事件目录数据集，以通过地震活动锐化在PRVIM上成像的结构，包括大北波多黎各断裂带、俯冲的北美板块，以及莫纳通道和Sombrero地震带可能的板块撕裂。此外，将使用FMTOMO程序进行三维断层成像，以对详细的地震速度结构进行成像，并帮助识别/证实与倾斜俯冲系统相关的重要地震特征。对这一研究相对不足的俯冲带进行详细的地震成像，将有助于深入了解这一斜缘的板块结构和动力学。地震重新定位和层析成像旨在提供PRVIM下俯冲板块结构的高分辨率图像，并确定两个地震群位置是否表示板块撕裂，类似于BOLIVAR项目在加勒比板块南侧成像的情况。高分辨率成像还将为未来的地球动力学模型提供地震约束。除了增加对斜俯冲带动力学的理解外，本提案的成果将允许识别PRVIM内最活跃的断层，特别是在大南波多黎各断裂带和大北波多黎各断裂带。因此，这将有助于更新波多黎各地震危险图的过程，该地图自2003年以来一直没有被美国地质调查局修订过。更新后的三维地震速度模型将用于确定当前波多黎各地震台网用于地震的一维速度模型是否需要更新。这项研究的结果将以短文形式在波多黎各大学mayagez网站和波多黎各地震网络推广材料中向公众展示，每年影响波多黎各各地数百名学生和教师。这项研究还将加强未被充分代表的学生和教师在地球科学领域的参与。波多黎各大学mayagez（西班牙裔服务机构）的硕士生将获得资助，作为他/她论文的一部分进行研究。学生和主要研究者还将在国家会议上展示他们的研究成果，并在同行评议的期刊上发表。