We present new P and S teleseismic tomography models of the upper mantle beneath California and Nevada. Improved tomographic methods and the incorporation of new data increase image resolution and seismic structure definition. Technical advancements include the use of 3-D ray tracing, ray weighting and finite-frequency sensitivity kernels. Together with the incorporation of modern crustal velocity models to account for crustal delay time, these tomographic advancements reveal slightly higher amplitudes and narrower structures beneath prominent tectonic features in California and Nevada. The addition of new data from the southern California Borderland and northwestern California are particularly useful. Based on our imaging results, we discuss the effects of temperature and partial melt on upper mantle seismic velocity beneath California and Nevada. We interpret the major seismically fast structures in our study area to be Juan de Fuca slab and its downward continuation beneath central Nevada and foundered Farallon lithosphere beneath the southern Sierra Nevada and Transverse Ranges. The seismically slow structures beneath the slab-free window of northern California Coast Range, the Salton Trough extensional basin, and the Cascadia back arc, are all consistent with the presence of partial melting of decompressing mantle. The imaged seismically fast and slow anomalies imply buoyancy variations and melt productivity that ultimately act on the overlying crust.

中文翻译：

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加利福尼亚和内华达下地幔上地幔的地震结构

我们提出了加利福尼亚和内华达州下方上地幔的新 P 和 S 远震断层扫描模型。改进的层析成像方法和新数据的结合提高了图像分辨率和地震结构定义。技术进步包括使用 3-D 光线追踪、光线加权和有限频率灵敏度内核。结合现代地壳速度模型来解释地壳延迟时间，这些层析成像的进步揭示了加利福尼亚和内华达州突出的构造特征下的振幅略高和结构更窄。添加来自南加州边境地区和加州西北部的新数据特别有用。根据我们的成像结果，我们讨论了温度和部分熔化对加利福尼亚和内华达下方上地幔地震速度的影响。我们将研究区域内的主要地震快速构造解释为 Juan de Fuca 板块及其在内华达中部下方的向下延续，以及内华达山脉南部和横向山脉下方的沉没法拉隆岩石圈。加利福尼亚海岸山脉北部无板窗、索尔顿海槽伸展盆地和卡斯卡迪亚后弧下方的地震缓慢结构都与减压地幔部分熔化的存在一致。成像的地震快慢异常意味着浮力变化和熔体生产力最终作用于上覆地壳。加利福尼亚海岸山脉北部无板窗、索尔顿海槽伸展盆地和卡斯卡迪亚后弧下方的地震缓慢结构都与减压地幔部分熔化的存在一致。成像的地震快慢异常意味着浮力变化和熔体生产力最终作用于上覆地壳。加利福尼亚海岸山脉北部无板窗、索尔顿海槽伸展盆地和卡斯卡迪亚后弧下方的地震缓慢结构都与减压地幔部分熔化的存在一致。成像的地震快慢异常意味着浮力变化和熔体生产力最终作用于上覆地壳。