We study ground-motion response in urban Los Angeles during the two largest events (M7.1 and M6.4) of the 2019 Ridgecrest earthquake sequence using recordings from multiple regional seismic networks as well as a subset of 350 stations from the much denser Community Seismic Network. In the first part of our study, we examine the observed response spectral (pseudo) accelerations for a selection of periods of engineering significance (1, 3, 6, and 8 s). Significant ground-motion amplification is present and reproducible between the two events. For the longer periods, coherent spectral acceleration patterns are visible throughout the Los Angeles Basin, while for the shorter periods, the motions are less spatially coherent. However, coherence is still observable at smaller length scales due to the high spatial density of the measurements. Examining possible correlations of the computed response spectral accelerations with basement depth and Vs30, we find the correlations to be stronger for the longer periods. In the second part of the study, we test the performance of two state-of-the-art methods for estimating ground motions for the largest event of the Ridgecrest earthquake sequence, namely three-dimensional (3D) finite-difference simulations and ground motion prediction equations. For the simulations, we are interested in the performance of the two Southern California Earthquake Center 3D community velocity models (CVM-S and CVM-H). For the ground motion prediction equations, we consider four of the 2014 Next Generation Attenuation-West2 Project equations. For some cases, the methods match the observations reasonably well; however, neither approach is able to reproduce the specific locations of the maximum response spectral accelerations or match the details of the observed amplification patterns.

我们使用来自多个区域地震台网以及更密集的社区的350个站的子集，研究了2019年Ridgecrest地震序列的两个最大事件（M7.1和M​​6.4）期间洛杉矶市区的地震动响应地震台网。在我们的研究的第一部分中，我们检查了观察到的响应频谱（伪）加速度，以选择具有工程意义的周期（1、3、6和8 s）。在两个事件之间存在显着的地面运动放大，并且可重现。对于较长的时间段，整个洛杉矶盆地可见相干的频谱加速度模式，而对于较短的时间段，运动在空间上的相干性较差。然而，由于测量的高空间密度，在较小的长度尺度上仍可观察到相干性。检验计算的响应频谱加速度与基底深度和Vs30的可能相关性，我们发现相关性在更长的时间内会更强。在研究的第二部分中，我们测试了两种用于估计Ridgecrest地震序列最大事件的地震动的最新技术的性能，即三维（3D）有限差分模拟和地震动预测方程式。对于仿真，我们对两个南加州地震中心3D社区速度模型（CVM-S和CVM-H）的性能感兴趣。对于地面运动预测方程，我们考虑了2014年下一代Attenuation-West2项目方程中的四个。在某些情况下，这些方法与观测值相当吻合。然而，