Development of the Eastern California Shear Zone — Walker Lane belt: The effects of microplate motion and pre-existing weakness in the Basin and Range
Development of the Eastern California Shear Zone — Walker Lane belt: The effects of microplate motion and pre-existing weakness in the Basin and Range
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DOI：
10.1016/j.tecto.2009.11.021
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发表时间：
2010-04
期刊：
影响因子：
2.9
通讯作者：
C. Plattner;R. Malservisi;K. Furlong;R. Govers
中科院分区：
文献类型：
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作者：
C. Plattner;R. Malservisi;K. Furlong;R. Govers
微板块运动在北美西部东加州剪切带形成中所起的作用尚不清楚。以前提出，与下加利福尼亚运动有关的切变从加州湾向北传播到内华达州。然而，有证据表明，东加州剪切带的形成早于下加利福尼亚运动的开始。因此，要么下加利福尼亚在6 Ma之前开始向西北方向移动，要么东加州剪切带是由不同于下加利福尼亚的微板块运动产生的剪切应变形成的。内华达州山脉运动对邻近剪切带发展的作用尚未得到证实。我们提出了一个数值模拟研究，探讨北美西部的变形响应下加利福尼亚和/或内华达州山脉微板块运动。特别是我们研究，如果，以及在什么条件下的微板块运动，剪切应变可以本地化的北方和南部的东加州剪切带（分离的Garlock故障）。我们发现，鉴于中新世盆地和山脉延伸（岩石圈强度对比或正断层）的预先存在的弱点，来自下加利福尼亚或内华达州微板块的剪切应变可以导致东加州剪切带的形成。此外，存在一个预先存在的弱点解释了早期启动的走向滑断层以北的加洛克故障。我们的模型表明，今天，下加利福尼亚微板块运动是主要的球员，为现今的变形率沿着东加州剪切带，并在过去的6 Myrs也是一个主要的驱动程序，应变本地化在南部东加州剪切带内的莫哈韦块。
The role that the motion of microplates has played in the development of the Eastern California Shear Zone in western North America is unclear. It was previously proposed that shear related to Baja California motion has propagated from the Gulf of California northward into Nevada. However, there is evidence that the formation of the Eastern California Shear Zone predates the inception of Baja California motion. Thus, either Baja California began to move northwestward prior to 6Ma, or the Eastern California Shear Zone formed by shear strain resulting from different microplate motion than Baja California. The role of Sierra Nevada motion on the development of an adjacent shear zone remains untested. We present a numerical modeling study that examines the deformational response of western North America to Baja California and/or Sierra Nevada microplate motion. In particular we study if, and under what condition of microplate motion, shear strain can localize in the northern and southern part of the Eastern California Shear Zone (separated by the Garlock fault). We find that given the pre-existing weakness from Miocene Basin and Range extension (a lithospheric strength contrast or normal faults) shear strain from either the Baja California or Sierra Nevada microplates can lead to the formation of the Eastern California Shear Zone. Furthermore, the presence of a pre-existing weakness explains the earlier initiation of strike-slip faulting north of the Garlock fault. Our models suggest that today, Baja California microplate motion is the major player for present-day deformation rates along the Eastern California Shear Zone and was in the past 6Myrs also a major driver of strain localization in southern Eastern California Shear Zone within the Mojave block.