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首页> 外文期刊>Pure and Applied Geophysics >Evidence of strain partitioning between the Sierra Madre fault and the Los Angeles Basin, southern California from numerical models
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Evidence of strain partitioning between the Sierra Madre fault and the Los Angeles Basin, southern California from numerical models

机译：基于数值模型的马德雷断裂与南加州洛杉矶盆地之间的应变分配证据

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摘要

Geodetic data indicate that the northern Metropolitan Los Angeles region is shortening at a rate of 4.5-6.0 mm/yr between downtown Los Angeles and the San Gabriel Mountains. If we assume that all of the uplift of the San Gabriel Mountains is due to the major frontal fault system (the Sierra Madre fault) and use reported values for bedrock uplift, slip per event and recurrence intervals to determine the slip rate on the Sierra Madre fault, we obtain slip rates between 0.6-1.27 mm/yr. Using these slip rates, the horizontal shortening attributable to the Sierra Madre fault accounts for only similar to33% of the observed shortening across the basin, leaving similar to67% of the shortening to be accounted for elsewhere. Herein we present a suite of models that test possible shortening mechanisms to account for this strain deficit. The models incorporate a range of fault geometries and have a layered structure with variable vertical and horizontal rheologies. The models demonstrate how lower-crust theology and the presence of a low rigidity, anelastically deforming sedimentary basin affects the dissipation of stress imposed on the viscous layers by elastic failure of the faults. We found that viscoelastic models with a single fault, vertically strong crust and a compliant sedimentary basin yield a horizontal velocity profile that best matches the geodetically observed velocity profile across the Los Angeles Basin. Our models also indicate that we are still not accounting for all of the observed deformation. Therefore, more complex models that include both laterally varying rheologies and frictional properties on faults must be considered.
机译：大地测量数据表明，洛杉矶市区和圣盖博山脉之间的北部都市圈地区以每年4.5-6.0毫米的速度缩短。如果我们假设圣盖博山的所有隆升都是由于主要的正面断层系统（塞拉马德雷断层）造成的，并使用报告的基岩隆起，每次滑动和复发间隔的值来确定塞拉马德雷的滑移率断层，我们获得的滑动率在0.6-1.27 mm / yr之间。使用这些滑移率，可归因于马德雷断裂的水平缩短量仅占整个盆地观测到的缩短量的33％，而其余67％的缩短量尚待其他地方考虑。本文中，我们提出了一套模型，用于测试可能的缩短机制以解决此菌株缺陷。这些模型包含了一系列的断层几何形状，并具有垂直和水平流变学可变的分层结构。这些模型证明了低地壳的神学和低刚度，非弹性变形沉积盆地的存在如何影响断层的弹性破坏施加在粘性层上的应力消散。我们发现具有单个断层，垂直坚硬的地壳和顺应性沉积盆地的粘弹性模型产生的水平速度剖面最匹配大地测量的整个洛杉矶盆地的速度剖面。我们的模型还表明，我们仍然没有考虑所有观察到的变形。因此，必须考虑更复杂的模型，包括横向变化的流变性和断层的摩擦特性。

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