Inelastic strain distribution and seismic radiation from rupture of a fault kink
Inelastic strain distribution and seismic radiation from rupture of a fault kink
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DOI：
10.1029/2008jb005847
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发表时间：
2008-12
影响因子：
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通讯作者：
B. Duan;S. Day
中科院分区：
文献类型：
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作者：
B. Duan;S. Day
[1] 我们扩展了弹动力有限元方法，将断层塑性屈服纳入动态地震破裂模型中。我们模拟了具有扭结（断层走向急剧变化）的断层模型的破裂，研究断层外塑性屈服如何影响破裂传播、地震辐射和近断层应变分布。我们发现，扭结处的高频辐射可以通过扭结附近的强塑性屈服来减少。高于几赫兹时，降低幅度非常显着。当破裂围绕扭结传播到受力较小的断层段时，塑性应变往往会局部化为带状和瓣状。非故障塑性屈服还显着降低了动态事件后扭结周围残余应力的不均匀性。计算出的扭结周围的塑性应变分布和来自扭结的辐射脉冲在计算可行的单元尺寸范围内几乎与网格无关。我们还发现，在没有像扭结这样的离散应力集中器的情况下，塑性应变有时会在破裂过程中沿着平面断层自发地局部化。在这种情况下，无量纲参数 T 表征了故障材料与其屈服强度的初始接近程度，决定了塑性应变是局部化为离散带还是平滑分布，大的 T 值促进局部化。然而，在自发局部化的情况下，剪切带的细节随着数值单元尺寸的变化而变化，这表明最终的塑性应变分布受到最短数值可解析尺度上发生的相互作用的影响。断层外塑性屈服也对破裂前沿的内聚区产生重要影响。
[1] We extend an elastodynamic finite element method to incorporate off-fault plastic yielding into a dynamic earthquake rupture model. We simulate rupture for models of faults with a kink (a sharp change in fault strike), examining how off-fault plastic yielding affects rupture propagation, seismic radiation, and near-fault strain distribution. We find that high-frequency radiation from a kink can be reduced by strong plastic yielding near the kink. The reduction is significant above several Hz. When rupture propagates around the kink onto a less favorably stressed fault segment, plastic strain tends to localize into bands and lobes. Off-fault plastic yielding also significantly reduces heterogeneity of residual stresses around the kink following a dynamic event. The calculated plastic strain distribution around the kink and the radiated pulse from the kink are nearly grid independent over the range of element size for which computations are feasible. We also find that plastic strain can sometimes localize spontaneously during rupture along a planar fault, in the absence of a discrete stress concentrator like the kink. In that case, a non-dimensional parameter T, characterizing the initial proximity of off-fault material to its yield strength, determines whether plastic strain localizes into discrete bands or is smoothly distributed, with a large value of T promoting localization. However, in the cases of spontaneous localization, the details of the shear banding change with numerical element size, indicating that the final plastic strain distribution is influenced by interactions occurring at the shortest numerically resolvable scales. Off-fault plastic yielding also makes an important contribution to the cohesive zone at the advancing edge of the rupture.