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: 2105358
• 负责人: Robert Clayton
• 金额: $ 21.86万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-15 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2105358&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.

下一次发生在圣安德烈亚斯断层南部的大地震预计将在加利福尼亚州洛杉矶以北数百公里处产生强烈的地面震动，这是因为地球表面下方的地质结构充当了将地震波引入波导的作用。研究表明，人们预期的地面运动可能比地震灾害模型预测的大四倍，这种差异可能会显着增加地震造成的损失，在规划抗震能力时也应考虑到这一点。在大洛杉矶地区。对地面震动的估计是由不完整的地球模型得出的，这些模型不能正确地代表引导地震能量的地质结构。在这里，研究人员利用在该地区进行的新型地震现场实验的记录建立了一个更详细的地球模型。 2017 年和 2020 年，研究人员在研究区域沿 10 条线布置了 700 多个现代仪器，使研究人员能够比以往更好地成像。他们改进和更新了区域地震速度的全套分析，并通过更新南加州地震中心社区来模拟预期的地面运动。速度模型；这是使用新开发的平台来完成的，该平台将高分辨率模型嵌入到更大规模的区域模型中，该研究结果改善了洛杉矶地区的地震灾害评估。代表性不足的小组以及路易斯安那州立大学和加州理工学院的研究生和本科生使用接收器函数，使用记录的几个远震事件 D) 剪切波速度来构建每条线的沿结构剖面。盆地的数据将通过表面波分析获得，该分析基于作为调查一部分部署的节点和宽带站之间的环境噪声相关性，以及该地区的南加州地震台网站，它们结合了剖面和 3-D 剪切波。他们利用环境噪声和当地地震产生衰减（QS 和 QP）模型，预期结果将是具有明确定义的基底界面和剪切力的盆地的 3D 地球模型。进一步，该团队将使用新模型模拟地震地面运动，并将强运动与通过噪声相关性预测的运动进行比较。团队尝试更先进的方法，包括水平集反演、自相关方法以及可能的全波形反演，这将首次将其中一些方法应用于这种特定类型的数据集。适用于世界上位于沉积盆地的其他主要城市，例如旧金山、西雅图、墨西哥城和利马。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Urban Basin Structure Imaging Based on Dense Arrays and Bayesian Array‐Based Coherent Receiver Functions

基于密集阵列和贝叶斯阵列的城市盆地结构成像——基于相干接收函数

• DOI: 10.1029/2021jb022279
• 发表时间: 2021-08
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Wang, Xin;Zhan, Zhongwen;Zhong, Minyan;Persaud, Patricia;Clayton, Robert W.
• 通讯作者: Clayton, Robert W.

Three‐Dimensional Basin Depth Map of the Northern Los Angeles Basins From Gravity and Seismic Measurements

根据重力和地震测量绘制的洛杉矶北部盆地三维盆地深度图

• DOI: 10.1029/2022jb025425
• 发表时间: 2023-07
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Villa, Valeria;Li, Yida;Clayton, Robert W.;Persaud, Patricia
• 通讯作者: Persaud, Patricia

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: 2023-07
• 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