Collaborative Research: Adjoint tomography of fault zone environments

合作研究：断层带环境的伴随断层扫描

• 批准号: 1314875
• 负责人: Yehuda Ben-Zion
• 金额: $ 7.43万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1314875&HistoricalAwards=false
• 关键词: Collaborative; Research; Adjoint; tomography; fault

We are investigating the subsurface structure of fault zones using a variety of seismic phases: surface waves, body waves, fault zone head waves, and fault zone trapped waves. By using a larger portion of the recorded seismic wavefield, we should be able to better resolve the fault zone structures to which the waves are sensitive. We use an adjoint-based tomographic inversion technique that relies on highly accurate, three-dimensional seismic wavefield simulations. The study has the following three components: (1) simulations of synthetic seismograms in realistic, complex 3D fault zone models, including clarifying the allowable ranges of geometrical and material variations that produce the observed characteristics of recorded head and trapped waves; (2) analysis of volumetric sensitivities of various fault zone, body, and surface phases to key fault zone structures at depth; (3) iterative adjoint tomographic inversions for the structures of the San Andreas fault near Parkfield and different sections of the San Jacinto fault zone.Large damaging earthquakes originate on faults kilometers below Earth's surface. A detailed characterization of the physical setting where earthquakes nucleate and rupture has not yet been achieved. By modeling seismic waves that are particularly sensitive to the structures of fault zones, we can image the subsurface structure of fault zones. The basic difficulty in imaging fault zones stems from their multi-scale and strong variations in structure, which are evident at the surface and within boreholes. By using accurate seismic wave propagation models, the study will provide the most detailed description of fault zone structure afforded by the recorded data. The project focuses on two societally relevant fault zones in southern California.

我们正在利用各种震相研究断层带的地下结构：表面波、体波、断层带头波和断层带陷波。通过使用记录的地震波场的较大部分，我们应该能够更好地解析波敏感的断层带结构。我们使用基于伴随的层析成像反演技术，该技术依赖于高精度的三维地震波场模拟。该研究由以下三个组成部分组成：(1) 在真实、复杂的 3D 断层带模型中模拟合成地震图，包括阐明产生记录的头波和陷波的观测特征的几何和材料变化的允许范围； （2）各类断裂带、体、地表相对深部关键断裂带构造的体积敏感性分析； (3) 对 Parkfield 附近的圣安德烈亚斯断层和圣哈辛托断层带不同部分的结构进行迭代伴随层析反演。大型破坏性地震起源于地球表面以下数公里的断层。尚未对地震成核和破裂的物理环境进行详细描述。通过对对断层带结构特别敏感的地震波进行建模，我们可以对断层带的地下结构进行成像。断层带成像的基本困难在于断层带的多尺度和强烈的结构变化，这在地表和钻孔内都很明显。通过使用精确的地震波传播模型，该研究将提供记录数据所提供的断层带结构最详细的描述。该项目重点关注南加州两个与社会相关的断层带。