Incorporating Amplitude Constraints in High Resolution Surface Wave Tomography of California

该项目将利用表面波的相位和振幅信息，开发加利福尼亚地壳和上地幔弹性结构的高分辨率、三维各向异性模型，以最大限度地提高分辨率。由于速度变化引起的聚焦和离焦引起的波幅变化携带的地震速度结构信息几乎与相位扰动一样多，但由于难以解释，振幅通常被忽略。通过仔细考虑其他影响振幅的因素，包括阵列外非均质性引起的散射或多径、衰减、现场响应和仪器响应，可以利用聚焦效应来改进速度模型。此外，固有的站点放大携带了关于站点下方和附近的速度结构的信息，这些信息可以直接纳入层析反演。拟谱数值模型将用于测试反演中使用的灵敏度核。来自新的地球范围观测站的数据将用于构建整个加利福尼亚和邻近内华达州部分地区的模型。监测站的高密度将产生低至数十公里尺度的横向变化的分辨率和低至约200公里深度的垂直结构的限制。感兴趣的构造目标包括勾勒出沃克巷地区和内华达山脉南部可能经历岩石圈分层的区域的形状，并确定圣安德烈亚斯断层附近各向异性层的厚度。更广泛的影响：研究生和本科生将通过直接参与拟议的研究，包括在项目过程中可能有几名女学生参与，来接受培训。结果将尽快与使用EarthScope数据的其他科学家共享，目的是建立合作，与其他观测结果联合解释表面波，包括体波断层扫描、剪切波分裂和接收函数分析。此外，通过EarthScope的工作，一旦获得图像和其他信息，将立即传播。

This project will develop high resolution, 3-D anisotropic models of the elastic structure of the crust and upper mantle beneath California using both phase and amplitude information of surface waves to maximize resolution. The variation in amplitude of waves due to focusing and defocusing caused by velocity variations carries nearly as much information about the seismic velocity structure as the phase perturbations, but amplitudes have generally been neglected due to the difficulty of interpreting them. By paying careful attention to other factors that affect amplitudes, including scattering or multipathing due to heterogeneities outside the array, attenuation, site response, and instrument response, the focusing effects can be employed to refine the velocity model. In addition, the intrinsic site amplification carries information about the velocity structure beneath and in the vicinity of the station that can be incorporated directly in the tomographic inversion. Pseudospectral numerical models will be employed to test the sensitivity kernels employed in the inversion. Data from new EarthScope stations will be used to construct models of all of California and parts of adjacent Nevada. The high density of stations will yield resolution of lateral variations on scales down to tens of kilometers and constraints on vertical structure down to depths of about 200 km. Tectonic goals of interest include outlining the shape of the area beneath the Walker Lane region and southern Sierra Nevada that may have experienced lithosphere delamination and determining the thickness of anisotropic layers in the vicinity of the San Andreas fault.Broader Impact: Graduate and undergraduate students will be trained through direct involvement in the proposed research, including the probable participation of several women students over the course of the project. Results will be shared as quickly as possible with other scientists using EarthScope data, with the intent of building collaborations for joint interpretation of surface waves with other observations, including body wave tomography, shear wave splitting, and receiver function analysis. In addition, working through EarthScope, images and other information will be disseminated as soon as they become available.