Understanding and modeling variability of ground motion is essential for building accurate and precise ground motion prediction equations, which can net site‐specific characterization and reduced hazard levels. Here, we explore the spatial variability in peak ground velocity (PGV) at Sage Brush Flats along the San Jacinto Fault in Southern California. We use data from a dense array (0.6 × 0.6 km², 1,108 geophones, station spacings 10–30 m) deployed in 2014 for ~1 month. These data offer an opportunity to study small‐scale variability in this region. We examine 38 earthquakes (2 ≤ M_L ≤ 4.2) within 200 km of the array. Fault strands and a small basin impact the ground motions, producing PGV variations up to 22% of the mean and a 40% reduction in P and S wave near‐surface velocities. We find along‐fault rupture directivity, source, and path effects can increase PGVs by 167%. Surface PGV measurements exceed the colocated borehole station (depth at 148 m) PGV by factors of 3–10, confirming the impact on PGV from near‐surface fault structures, basins, topography, and amplifications from soft sediments. Consistently, we find high PGVs within the basin structure. A pair of colocated GaM_L2.6 events produce repeatable PGV values with similar spatial patterns. The average corner frequencies of these two events are 11–16 Hz, and viable measurements of stress drop can differ by 6.45 MPa. Within this small array, the PGV values are variable implying spatial extrapolation of PGV to regions of known faults and basins, even across a small area, should be done with caution.

中文翻译：

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南加州密集地震阵列揭示的峰值地速空间变异性

了解地面运动的可变性并对其进行建模对于建立准确而精确的地面运动预测方程至关重要，该方程可以实现针对特定地点的特征描述并降低危害等级。在这里，我们探索了南加州圣哈辛托断层的鼠尾草平地的峰值地面速度（PGV）的空间变异性。我们使用从密集阵列（0.6×0.6公里数据²，1108个地震检波器，站间距10-30米）部署在2014年〜1个月。这些数据为研究该地区的小规模变化提供了机会。我们研究38级地震（2≤中号_大号 阵列200公里内≤4.2）。断层和一个小的盆地影响地面运动，导致PGV变化高达平均值的22％，P和P降低40％S波近地表速度。我们发现，沿断层破裂的方向性，震源和路径影响可以使PGV增加167％。地表PGV的测量值比同位置的钻孔站PGV（深度148 m）超出3-10倍，证实了近地表断层结构，盆地，地形和软沉积物放大对PGV的影响。一致地，我们在盆地结构中发现了较高的PGV。一对并置的GaM _L2.6事件产生具有相似空间模式的可重复PGV值。这两个事件的平均转折频率为11–16 Hz，可行的应力降测量值相差6.45 MPa。在这个小的阵列中，PGV值是可变的，这意味着PGV的空间外推到已知断层和盆地的区域，即使是很小的区域，也应谨慎行事。