Active Dipping Interface of the Southern San Andreas Fault Revealed by Space Geodetic and Seismic Imaging
Active Dipping Interface of the Southern San Andreas Fault Revealed by Space Geodetic and Seismic Imaging
复制标题
DOI：
10.1029/2023jb026811
复制
发表时间：
2023-10
期刊：
影响因子：
--
通讯作者：
Ellis J. Vavra;H. Qiu;Benxin Chi;P. Share;A. Allam;Matthias Morzfeld;Frank Vernon;Y. Ben‐Zion;Y. Fialko
中科院分区：
文献类型：
--
作者：
Ellis J. Vavra;H. Qiu;Benxin Chi;P. Share;A. Allam;Matthias Morzfeld;Frank Vernon;Y. Ben‐Zion;Y. Fialko
位于加州的南圣安德烈亚斯断层（SSAF）是世界上研究最透彻的断层之一，但其在科切拉山谷孕震深度的构造仍然是个谜。我们使用空间大地测量和地震观测相结合的方法来证明，SSAF的相对较直的最南端，在千棕榈和孟买海滩之间，在整个上地壳（<10 km），包括浅的东亚地层，以60-80°的角度向东北倾斜。我们使用与浅层蠕动相关的表面位移反演以及来自穿过千棕榈附近断层轨迹的密集节点阵列的地震数据来限制顶部2-3公里处的断层产状。资料反演表明，浅倾构造在深部与地震活动丛集相连接，表明存在连续贯通的断层面。倾斜断层几何形状对长期断层滑动速率、未来大地震期间地面震动强度以及南部SAF的有效强度具有重要影响。
The Southern San Andreas Fault (SSAF) in California is one of the most thoroughly studied faults in the world, but its configuration at seismogenic depths remains enigmatic in the Coachella Valley. We use a combination of space geodetic and seismic observations to demonstrate that the relatively straight southernmost section of the SSAF, between Thousand Palms and Bombay Beach, is dipping to the northeast at 60–80° throughout the upper crust (<10 km), including the shallow aseismic layer. We constrain the fault attitude in the top 2–3 km using inversions of surface displacements associated with shallow creep, and seismic data from a dense nodal array crossing the fault trace near Thousand Palms. The data inversions show that the shallow dipping structure connects with clusters of seismicity at depth, indicating a continuous throughgoing fault surface. The dipping fault geometry has important implications for the long‐term fault slip rate, the intensity of ground shaking during future large earthquakes, and the effective strength of the southern SAF.