Detailed seismic imaging and monitoring of the subsurface material around the San Jacinto fault zone

圣哈辛托断层带周围地下物质的详细地震成像和监测

基本信息

批准号：
1620601
负责人：
Yehuda Ben-Zion
金额：
$ 25.22万
依托单位：
University of Southern California
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-07-01 至 2019-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1620601&HistoricalAwards=false
关键词：
Detailed seismic imaging monitoring subsurface

项目摘要

This study develops and uses advanced seismological techniques and continuous waveform data recorded by spatially-dense fault zone arrays around the San Jacinto Fault Zone (SJFZ) in southern California. Analyses of these data provide detailed characterization of (potentially time-dependent) seismic velocities and attenuation coefficients of the shallow crust. To provide benchmarks for the new techniques and understand how seismic properties change with location and depth, the investigators use data recorded by shallow borehole seismometers installed within and adjacent to the fault zone, as well as recordings from regional seismic networks. These results complement models of tomographic studies that typically do not resolve seismic properties in the shallow crust, and allow development of seismic structural models around the SJFZ essentially up to the surface. Knowledge of seismic properties of the shallow crust is particularly relevant to observed ground motion and failure processes. These results may be relevant to numerous other applications including crustal hydrology, geothermal energy, subsurface reservoirs and storage, as well as seismic safety of infrastructure facilities. The analysis methods develop by this research can be used in studies of seismic properties of the subsurface material in other locations. The research uses state-of-the-art data and novel seismic imaging and monitoring techniques to close critical observational gaps. The studies address the following key questions: (1) What are the seismic velocities and attenuation coefficients in the top few hundred meters of the crust at various sections of the SJFZ and at sites that are off the fault? (2) At what stress/strain amplitudes do shallow rocks have nonlinear response and temporal changes of properties in relation to different loading mechanisms and periods (e.g., local and remote earthquakes, tides, and seasonal variations) and location with respect to the fault zone, site condition parameters, and depth? (3) How do amplitudes of temporal changes of seismic properties and recovery timescales produced by various loadings vary in relation to the fault zone, site conditions and depth? (4) Are there fault sections and/or off-fault sites with higher susceptibly to failures (manifested by time-dependent seismic properties), and if they are found, can anomalous properties in these regions be identified that may explain the elevated susceptibility? The studies can augment significantly the available in situ characterization of seismic velocity and attenuation coefficients, nonlinear response and temporal changes of properties in the top few hundred meters of the crust. The results are expected to provide fundamental information that may lead to improved understanding of seismic ground motion (and hence shaking hazard) as well as other applications.

这项研究开发并使用了先进的地震学技术和由南加州圣哈辛托断层带 (SJFZ) 周围的空间密集断层带阵列记录的连续波形数据。对这些数据的分析提供了（可能与时间相关的）地震速度和浅地壳衰减系数的详细特征。为了为新技术提供基准并了解地震特性如何随位置和深度变化，研究人员使用安装在断层带内和附近的浅井地震仪记录的数据以及区域地震网络的记录。这些结果补充了通常无法解析浅地壳地震特性的层析成像研究模型，并允许开发 SJFZ 周围基本上直至地表的地震结构模型。对浅地壳地震特性的了解与观测到的地面运动和破坏过程特别相关。这些结果可能与许多其他应用相关，包括地壳水文学、地热能、地下水库和储存以及基础设施的地震安全。本研究开发的分析方法可用于研究其他地点地下材料的地震特性。该研究使用最先进的数据和新颖的地震成像和监测技术来缩小关键的观测差距。研究解决了以下关键问题：（1）SJFZ各断层和断层外地壳顶部几百米的地震速度和衰减系数是多少？ (2) 在什么应力/应变幅度下，浅层岩石具有与不同加载机制和周期（例如，本地和远程地震、潮汐和季节变化）以及相对于断裂带的位置相关的非线性响应和特性的时间变化、场地条件参数、深度？ (3) 不同荷载产生的地震特性随时间变化的幅度和恢复时间尺度如何随断层带、场地条件和深度变化？ (4) 是否存在更容易发生故障的断层段和/或断层外地点（通过与时间相关的地震特性来表现），如果发现，是否可以识别这些区域中的异常特性来解释敏感性升高的原因？这些研究可以显着增强对地壳顶部几百米的地震速度和衰减系数、非线性响应和特性随时间变化的可用现场表征。预计结果将提供基本信息，可能有助于提高对地震地面运动（以及由此产生的震动危险）以及其他应用的理解。