We use UAVSAR interferograms to characterize fault slip, triggered by the Mw 7.2 El Mayor-Cucapah earthquake on the 1 San Andreas Fault in the Coachella Valley providing comprehensive maps of short-term geodetic surface deformation that complement in situ measurements. Creepmeters and geological mapping of fault offsets on Durmid Hill recorded 4 and 8 mm of average triggered slip respectively on the fault, in contrast to radar views that reveal significant off-fault dextral deformation averaging 20 mm. Unlike slip in previous triggered slip events on the southernmost San Andreas fault, dextral shear in 2010 is not confined to transpressional hills in the Coachella valley. Edge detection and gradient estimation applied to the 50-m-sampled interferogram data identify the location (to 20 m) and local strike (to <4°) of secondary surface ruptures. Transverse curve fitting applied to these local detections provides local estimates of the radar-projected dextral slip and a parameter indicating the transverse width of the slip, which we equate with the depth of subsurface shear. These estimates are partially validated by fault-transverse interferogram profiles generated using the GeoGateway UAVSAR tool, and appear consistent for radar-projected slip greater than about 5 mm. An unexpected finding is that creep and triggered slip on the San Andreas fault terminate in the shallow subsurface below a surface shear zone that resists the simple expression of aseismic fault slip. We introduce the notion of a surface locking depth above which fault slip is manifest as distributed shear, and evaluate its depth as 6–27 m.

中文翻译：

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无人机SAR揭示2010年El Mayor Cucapah地震引发的圣安德烈亚斯断层最南端的埋藏抗震滑移和断层外变形


我们使用 UAVSAR 干涉图来表征由科切拉山谷 1 San Andreas 断层上的 Mw 7.2 El Mayor-Cucapah 地震引发的断层滑动特征，提供短期大地表面变形的综合地图，以补充现场测量。 Durmid Hill 断层偏移的蠕变仪和地质测绘分别记录了断层上 4 毫米和 8 毫米的平均触发滑移，而雷达图像显示平均 20 毫米的显着断层右旋变形。与之前在最南端的圣安德烈亚斯断层触发的滑移事件中的滑移不同，2010 年的右旋切变并不局限于科切拉山谷的压压丘陵。应用于 50 m 采样干涉图数据的边缘检测和梯度估计可识别二次表面破裂的位置（至 20 m）和局部走向（至 <4°）。应用于这些局部检测的横向曲线拟合提供了雷达投影的右旋滑移的局部估计以及指示滑移横向宽度的参数，我们将其等同于地下剪切的深度。这些估计得到了使用 GeoGateway UAVSAR 工具生成的断层横向干涉图剖面的部分验证，并且对于大于约 5 毫米的雷达投影滑移似乎是一致的。一个意想不到的发现是，圣安德烈亚斯断层上的蠕变和触发滑移终止于地表剪切带下方的浅层地下，该剪切带抵抗了地震断层滑移的简单表达。我们引入了地表锁定深度的概念，在该深度以上断层滑移表现为分布剪切，并评估其深度为6-27 m。