Collaborative Research: A New 3-D Velocity and Structural Model of the Northern Basins in the Los Angeles Region for Improved Ground Motion Estimates

合作研究：洛杉矶地区北部盆地的新 3D 速度和结构模型，用于改进地震动估计

• 批准号: 2317154
• 负责人: Patricia Persaud
• 金额: $ 20.46万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-01-15 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2317154&HistoricalAwards=false
• 关键词: Collaborative; Research; New; Velocity; Structural

The next large earthquake on the southern San Andreas fault is expected to produce strong ground shaking hundreds of kilometers to the north, in Los Angeles, California. This will occur because the geologic structures beneath the Earth’s surface act as a wave guide channeling earthquake waves into downtown Los Angeles. It has been shown that the ground motions one can expect could be a factor of four larger than what earthquake hazard models predict. This difference may significantly increase damages resulting from earthquakes. It should also be accounted for when planning for earthquake resilience in the greater Los Angeles area. The inaccurate estimates for ground shaking result from incomplete Earth models which do not properly represent the geologic structures that channel seismic energy. Here, the researchers build a more detailed Earth model of the region. They use recordings from a new style of seismic field experiment carried out between 2017 and 2020; it consisted of laying out more than 700 modern instruments along 10 lines across the study area. This dense geometry allows the team to image better than ever before the subterranean structures channeling earthquake energy. The researchers carry out a full suite of analyses of the dense dataset. They refine and update models for regional seismic velocity. They simulate expected ground motions accounting for the new findings. The new Earth models are made available to the scientific community by updating the Southern California Earthquake Center community velocity models; this is done using a newly developed platform for embedding high-resolution models into larger-scale regional models. Results of the study improve seismic hazard assessment in the Los Angeles area. This collaborative project also supports a female early-career scientist from an underrepresented group, and graduate and undergraduate students at Louisiana State University and the California Institute of Technology. The researchers use receiver functions to construct profiles of the structure along each of the lines, using several teleseismic events that were recorded. The three-dimensional (3-D) shear wave velocities for the basins will be obtained from surface wave analysis based on ambient noise correlation between the nodes and broadband stations that were deployed as part of the survey, and the Southern California Seismic Network stations in the region. They combine the profiles and 3-D shear wave velocity estimates by using the gravity data across the basins. They produce attenuation (QS and QP) models from ambient noise and local earthquakes. The expected result will be a 3-D Earth model for the basins with a well-defined basement interface and shear wave velocities down through the sedimentary layers obtained at a higher resolution than existing models. As a further step, the team will simulate earthquake ground motions with the new model and compare strong motions to those predicted from noise correlations. The unique geometry of the survey allows the team to try more advanced methods including level-set inversion, autocorrelation methods, and possibly full waveform inversion. This advances the application of some of these methodologies for the first time to this particular type of data set. The full suite of methodologies developed here will be applicable other major cities around the world that are located on sedimentary basins such as San Francisco, Seattle, Mexico City and Lima.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.

预计南部圣安德烈亚斯（San Andreas）断层的下一次大地震将产生强烈的地面，摇晃在加利福尼亚州洛杉矶的北部数百公里。之所以发生这是因为地球表面下方的地质结构是将地震波传播到洛杉矶市中心的波浪指南。已经表明，人们期望的地面运动比地震危害模型预测的要素大四个。这种差异可能会大大增加地震造成的损害。计划在大洛杉矶地区计划地震弹性时也应考虑在内。地面模型不正确地代表通向地震能量的地质结构的不准确震动的估计不准确。在这里，研究人员建立了该地区更详细的地球模型。他们使用了2017年至2020年之间进行的新型地震田间实验的记录；它包括在整个研究区域沿10条线铺设700多种现代乐器。这种密集的几何形状使团队比以前的地下结构引导地震能量更好。研究人员对密集数据集进行了完整的分析。他们完善并更新区域地震速度的模型。他们模拟了有关新发现的预期地面运动。新的地球模型可通过更新南加州地震中心社区速度模型提供给科学界。这是使用新开发的平台将高分辨率模型嵌入大型区域模型中的。该研究的结果改善了洛杉矶地区的地震危险评估。这个合作项目还支持一位女性早期的医生科学家，来自代表性不足的小组，路易斯安那州立大学和加利福尼亚理工学院的研究生和本科生。研究人员使用接收器函数沿每条线路构建结构的曲线，并使用记录的几个远程宣传事件。低音的三维（3-D）剪切波速度将基于表面波分析，基于节点和宽带站之间的环境噪声相关性，这些速度与该地区的南加州地震网站部署了。它们通过使用低音的重力数据结合了曲线和3-D剪切波速度的估计。它们从环境噪声和当地地震中产生衰减（QS和QP）模型。预期的结果将是一个3-D地球模型，该模型具有明确定义的地下室界面和剪切波速度的速度，并通过比现有模型更高的分辨率获得的沉积层。为了进一步，团队将使用新模型模拟地震地面运动，并将强大动作与噪声相关性预测的动作进行比较。调查的独特几何形状使团队可以尝试更高级的方法，包括级别倒置，自相关方法和可能的完整波形反演。这首先将其中一些方法应用于此特定类型的数据集。此处开发的完整方法将适用于全球其他主要城市，这些城市位于旧金山，西雅图，西雅图，墨西哥城和利马等沉积贝司上。这奖反映了NSF的法定任务，并被认为是通过基金会的知识分子和更广泛的影响审查审查标准来通过评估来通过评估来支持的。

项目成果

Basin Depth Model for the BASIN Project

BASIN 项目的盆地深度模型

• DOI: 10.22002/d1.20252
• 发表时间: 2022
• 期刊: CaltechDATA

Earth model-space exploration in Southern California: Influence of topography, geotechnical layer, and attenuation on wavefield accuracy

地球模型-南加州空间探索：地形、岩土层和衰减对波场精度的影响

• DOI: 10.3389/feart.2022.964806
• 发表时间: 2022
• 期刊: Frontiers in Earth Science
• 影响因子: 2.9
• 作者: Ajala, Rasheed;Persaud, Patricia;Juarez, Alan
• 通讯作者: Juarez, Alan

Shear Wave Velocities in the San Gabriel and San Bernardino Basins, California

加利福尼亚州圣盖博盆地和圣贝纳迪诺盆地的剪切波速度

• DOI: 10.1029/2023jb026488
• 发表时间: 2023
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Li, Yida;Villa, Valeria;Clayton, Robert W.;Persaud, Patricia
• 通讯作者: Persaud, Patricia

Ground-Motion Evaluation of Hybrid Seismic Velocity Models

混合地震速度模型的地震动评估

• DOI: 10.1785/0320220022
• 发表时间: 2022
• 期刊: The Seismic Record
• 作者: Ajala, Rasheed;Persaud, Patricia
• 通讯作者: Persaud, Patricia