Tectonic Inheritance During Plate Boundary Evolution in Southern California Constrained From Seismic Anisotropy
Tectonic Inheritance During Plate Boundary Evolution in Southern California Constrained From Seismic Anisotropy
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DOI：
10.1029/2021gc010099
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发表时间：
2021-08
期刊：
影响因子：
3.7
通讯作者：
V. Schulte‐Pelkum;T. Becker;W. Behr;M. Miller
中科院分区：
文献类型：
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作者：
V. Schulte‐Pelkum;T. Becker;W. Behr;M. Miller
对流力传递到板块的方式以及板块边界内部和下方的应变局部化仍然存在争议。为了解决一些相关问题，我们分析了南加州从地表到软流层的一系列变形指标。目前的表面应变率可以从大地测量学中推断出来。在发震地壳深处，应力可以通过震源机制和局部地震剪切波的分裂，通过裂缝相关的地震速度来推断。在更深的深度，通过接收函数各向异性、Pn和P层析成像、面波层析成像、SKS和其他远震岩心相的分裂，可以获得对岩石组构的约束。我们构建了一个变形相关观测的综合，侧重于变形风格的定量比较。在近地表和软流圈地幔中，我们发现了大致的N - S压缩和E - W伸展的一致性。然而，所有岩石圈各向异性指标都显示出与这种模式的偏差。接收函数的Pn快速轴和倾斜叶理是断层平行的，没有断层轨迹的定位，与西部横向山脉的后法拉隆块体旋转相匹配。局部横波分裂方向在很大程度上偏离了震源机制推断的应力方向。我们认为这些观测结果表明，在Farallon俯冲和随后的伸展期间发育的岩石圈结构尚未完全被现今的转换运动重置，并可能影响当前的变形行为。这为研究变形记忆和岩石圈-软流圈相互作用的时间尺度提供了新的视角。
The style of convective force transmission to plates and strain‐localization within and underneath plate boundaries remain debated. To address some of the related issues, we analyze a range of deformation indicators in southern California from the surface to the asthenosphere. Present‐day surface strain rates can be inferred from geodesy. At seismogenic crustal depths, stress can be inferred from focal mechanisms and splitting of shear waves from local earthquakes via crack‐dependent seismic velocities. At greater depths, constraints on rock fabrics are obtained from receiver function anisotropy, Pn and P tomography, surface wave tomography, and splitting of SKS and other teleseismic core phases. We construct a synthesis of deformation‐related observations focusing on quantitative comparisons of deformation style. We find consistency with roughly N‐S compression and E‐W extension near the surface and in the asthenospheric mantle. However, all lithospheric anisotropy indicators show deviations from this pattern. Pn fast axes and dipping foliations from receiver functions are fault‐parallel with no localization to fault traces and match post‐Farallon block rotations in the Western Transverse Ranges. Local shear wave splitting orientations deviate from the stress orientations inferred from focal mechanisms in significant portions of the area. We interpret these observations as an indication that lithospheric fabric, developed during Farallon subduction and subsequent extension, has not been completely reset by present‐day transform motion and may influence the current deformation behavior. This provides a new perspective on the timescales of deformation memory and lithosphere‐asthenosphere interactions.