We present deterministic ground motion simulations that account for the cyclic multiaxial response of sediments in the shallow crust. We use the Garner Valley in Southern California as a test case. The multiaxial constitutive model is based on the bounding surface plasticity theory in terms of total stress and is implemented in a high‐performance computing finite‐element parallel code. A major advantage of this model is the small number of free parameters that need to be calibrated given a shear modulus reduction curve and the ultimate soil strength. This, in turn, makes the model suitable for regional‐scale simulations, where geotechnical data in the shallow crust are scarce. In this paper, we first describe a series of numerical experiments designed to verify the model implementation. This is followed by a series of idealized large‐scale simulations in a 35 x 26 x 4.5 km³ domain that encompasses the Garner Valley downhole array site, which is an instrumented and well‐characterized site in Southern California. Material properties were extracted from the Southern California Earthquake Center Community velocity model, CVM‐S4.26, considering its optional geotechnical layer, while the modulus reduction curves and soil strength were selected empirically to constrain the nonlinear soil model parameters. Our nonlinear simulations suggest that peak ground displacements within the valley increase relative to the linear case, while peak ground accelerations can increase or decrease, depending on the frequency content of the excitation. The comparisons of our simulations against hybrid three‐dimensional–one‐dimensional site response analyses suggest the inadequacy of the latter to capture the complexity of fully three‐dimensional simulations.

中文翻译：

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南加州加纳谷浅层地壳非线性确定性地面运动模拟

我们提出了确定性地面运动模拟，该模拟解释了浅地壳中沉积物的循环多轴响应。我们使用南加州的 Garner Valley 作为测试案例。多轴本构模型基于总应力方面的边界面塑性理论，并在高性能计算有限元并行代码中实现。该模型的一个主要优点是在给定剪切模量降低曲线和极限土壤强度的情况下需要校准的自由参数数量较少。这反过来又使该模型适用于区域尺度模拟，其中浅地壳中的岩土工程数据稀缺。在本文中，我们首先描述了一系列旨在验证模型实现的数值实验。随后在 35 x 26 x 4.5 km³ 域中进行了一系列理想化的大规模模拟，该域包含 Garner Valley 井下阵列站点，该站点是南加州一个仪器齐全且特征明确的站点。考虑到可选的岩土层，从南加州地震中心社区速度模型 CVM-S4.26 中提取材料特性，同时根据经验选择模量降低曲线和土壤强度以约束非线性土壤模型参数。我们的非线性模拟表明谷内的峰值地面位移相对于线性情况增加，而峰值地面加速度可以增加或减少，具体取决于激励的频率内容。