Collaborative Research: A 3D Seismic Study of the Pacific-North American Plate Boundary in Southern California

合作研究：南加州太平洋-北美板块边界的 3D 地震研究

• 批准号: 0824982
• 负责人: Dayanthie Weeraratne
• 金额: $ 22.26万
• 依托单位: The University Corporation, Northridge
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0824982&HistoricalAwards=false
• 关键词: Collaborative; Research; 3D; Seismic; Study

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Intellectual Merit: The Pacific-North America plate boundary in southern California is one of the only examples of recorded subduction of an oceanic spreading center in geological history, but this process is likely to be a common component of Earth history. Almost half of the Pacific-North America plate boundary in southern California lies offshore, but little is known about the physical properties of the oceanic plate, its mode of deformation, or its influence on western North America. This project will deploy 24 long-duration, broadband Ocean Bottom Seismometers (OBS) in a passive seismic experiment off the coast of southern California that spans the oceanic half of the Pacific-North America plate boundary. The OBS data will be combined with same-event data recorded on the permanent California Integrated Seismic Network for coverage across the onshore basins, San Andreas fault, and into the North America plate. The objective is to understand the tectonic interaction at this boundary by identifying the physical properties and deformation styles of the Pacific plate and near-shore microplates, as well as distinguish among contrasting upper mantle geodynamic scenarios which predict large-scale mantle flow patterns beneath western North America. The seismic studies aim to characterize the driving plate motion consequences of collision between the rift system, a fragmented subducted plate, the lengthening of the San Andreas transform fault system, and block rotations. Of particular relevance is understanding the source of the forces and rheology that affect the stress state of the elastic crust to generate earthquakes. The boundaries for the seismic array overlap the region of complex breakup and fracture of the Pacific plate near-shore where several microplates are observed, and extends far to the west to provide comparison with oceanic lithosphere that is not fractured and has formed at a uniform rate. The results will aid in understanding the boundary forces due to relative plate motions, the driving forces and characteristics of oceanic and continental scale deformation, and how the continental margin accretionary process is influenced by offshore tectonics. An additional goal is to examine the local earthquake data and their focal mechanisms for seismicity patterns. The local seismicity recorded by the proposed OBS network is expected to produce a more accurate offshore hypocenter catalog that can be used to identify spatial relationships between background seismic activity with mapped offshore faultsBroader Impacts: The broader impacts will be carried out through activities that include a partnership with the Southern California Marine Institute to create hands-on scientific opportunities and educational materials. These materials will incorporate the OBS data and general offshore seismology into programs for high school and college students. Undergraduate and graduate students will participate in the research cruises, scientific analysis, and related teaching activities. Masters and undergraduate level students from Cal State Northridge, a designated Minority Serving Institution, will include women and minority students through the Catalyst program which recruits actively for minorities in geology and geophysics. Data from the experiment will be archived at the IRIS Data Management Center and the Southern California Earthquake Data Center, both of which are multi-user data archival facilities that are open to data requests from other scientists, students, and non-scientists. The local earthquake data collection portion of this experiment will enhance the understanding of hazardous offshore seismic structures in applications that can directly benefit society. The offshore background seismicity catalog will elucidate the activity of offshore faults. Local earthquake phase data will contribute to an updated 3D crustal seismic velocity model that extends offshore to be used by researchers to carry out 3D wave propagation simulations to estimate the amount and effects of shaking on nearby coastal communities for use in mitigation efforts.

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。智力上的优点：南加州的太平洋-北美板块边界是地质史上仅有的有记录的海洋扩张中心俯冲的例子之一，但这个过程很可能是地球历史的一个共同组成部分。加利福尼亚州南部的太平洋-北美板块边界几乎有一半位于近海，但人们对海洋板块的物理性质、其变形模式或其对北美西部的影响知之甚少。该项目将在加利福尼亚州南部海岸外的被动地震实验中部署24台长时间、宽带海底地震仪(OBS)，该实验跨越太平洋-北美板块边界的大洋一半。OBS数据将与加州永久综合地震网络上记录的相同事件数据相结合，覆盖整个陆上盆地、圣安德烈亚斯断层和北美板块。其目的是通过识别太平洋板块和近岸微板块的物理性质和变形方式，以及区分预测北美西部下方大规模地幔流动模式的不同上地幔地球动力学情景，来了解这一边界上的构造相互作用。地震研究的目的是描述裂谷系统、破碎的俯冲板块、圣安德烈亚斯变换断层系统的拉长和块体旋转之间的碰撞对驱动板块运动的影响。特别相关的是了解影响弹性地壳应力状态以产生地震的力和流变学的来源。地震台阵的边界与太平洋板块近岸复杂解体和破裂的区域重叠，在那里观察到几个微板块，并向西延伸很远，以提供与没有破裂且以统一速度形成的大洋岩石圈的对比。这些结果将有助于理解相对板块运动所产生的边界力、大洋和大陆尺度变形的驱动力和特征，以及近海构造如何影响大陆边缘的沉积过程。另一个目标是检查当地的地震数据及其地震活动模式的震源机制。由拟议的OBS网络记录的当地地震活动预计将产生更准确的近海震源目录，可用于确定背景地震活动与绘制的近海断层之间的空间关系影响：将通过与南加州海洋研究所建立伙伴关系等活动来实施更广泛的影响，以创造实际操作的科学机会和教育材料。这些材料将把OBS数据和一般近海地震学纳入针对高中生和大学生的课程。本科生和研究生将参加研究巡航、科学分析和相关教学活动。加州州立大学北岭分校是一所指定的少数民族服务机构，该校的硕士和本科生将包括女性和少数民族学生，该计划通过Catalyst计划积极为少数族裔招募地质学和地球物理学专业的学生。来自实验的数据将在IRIS数据管理中心和南加州地震数据中心存档，这两个中心都是多用户数据存档设施，对其他科学家、学生和非科学家的数据请求开放。这项实验的当地地震数据收集部分将加强对危险近海地震结构在应用中的理解，这些应用可以直接造福社会。近海背景地震活动目录将阐明近海断裂的活动性。当地地震震相数据将有助于更新的三维地壳地震速度模型，该模型延伸到近海，供研究人员用来进行三维波传播模拟，以估计震动对附近沿海社区的数量和影响，用于缓解工作。