Kinematics and Evolution of the Southern Eastern California Shear Zone, Based on Analysis of Fault Strike, Distribution, Activity, Roughness, and Secondary Deformation
Kinematics and Evolution of the Southern Eastern California Shear Zone, Based on Analysis of Fault Strike, Distribution, Activity, Roughness, and Secondary Deformation
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DOI：
10.1029/2021tc006859
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发表时间：
2021-10
期刊：
影响因子：
4.2
通讯作者：
J. Spotila;Max M. Garvue
中科院分区：
文献类型：
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作者：
J. Spotila;Max M. Garvue
东加州剪切带是一组复杂的右旋断层，可容纳显着的板块运动并产生大地震。该系统的演化以及为什么它由密集的、不规则的断层组成，并在多断层破裂中破裂，目前尚不清楚。在这里，我们分析了莫哈韦地块南部右旋断层的几何形状、空间分布和第四纪滑动活动。我们发现这些断层的方向有利于适应区域右旋板块运动，并且在逆时针旋转到不利位置后没有显示出更替的证据，尽管活动可能如先前提出的那样向西迁移。我们还证实，剪切带具有压折性，具有广泛的约束弯曲、分布的会聚变形，并对近断层地形产生显着影响。观测还表明，断层在几何上是复杂的，如断层走向的沿走向变化所代表的那样。我们记录了走向变化和断层活动（滑移率或净滑移）之间的相关性，这在剪切带以及其他断层的对照组中很明显。我们认为走向变异性代表了一种几何粗糙度的形式，它可能抑制断层滑动并导致复杂的破裂、滑动强化行为和普遍的断层变形。其他因素，包括预先存在的地壳结构、边缘效应和应力场的变化，可能会使运动学进一步复杂化。这些结果表明，剪切带的断层仍然很年轻，并且有些独特，但为了解广泛分布的剪切如何演化为贯穿的大陆转换系统提供了一个重要的窗口。
The Eastern California shear zone is a complex set of dextral faults that accommodates significant plate motion and has produced large earthquakes. The evolution of this system and why it consists of closely spaced, irregular faults that fail in multi‐fault ruptures are not well understood. Here we analyze the geometry, spatial distribution, and Quaternary slip activity of right‐lateral faults in the southern Mojave block. We find these faults are oriented favorably for accommodating regional dextral plate motion and do not show evidence of replacement following counterclockwise rotation to unfavorable positions, although activity may be migrating westward as previously proposed. We also confirm that the shear zone is transpressive, with widespread restraining bends, distributed convergent deformation, and significant impact on near‐fault topography. Observations also show that faults are geometrically complex, as represented by along‐strike variability in fault strike. We document a correlation between strike variability and fault activity (slip rate or net slip), which is evident within the shear zone as well as for a control group of other faults. We suggest that strike variability represents a form of geometric roughness, which may inhibit fault slip and result in complex ruptures, slip‐strengthening behavior, and a prevalence of off‐fault deformation. Other factors, including preexisting crustal fabric, edge effects, and changes in the stress field, may further complicate kinematics. These results suggest that faults of the shear zone are still juvenile and somewhat unique, yet offer an important window into how broadly distributed shear may evolve into a through‐going continental transform system.