Seismic source dynamics, heterogeneity and friction
Seismic source dynamics, heterogeneity and friction
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震源动力学、非均质性和摩擦力
DOI：
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
A. Cochard
中科院分区：
文献类型：
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作者：
R. Madariaga;A. Cochard
最近有几位作者提出，活动断层周围的应力分布可能自发地成为临界应力。其他作者认为，不均匀性是断层面的永久特征。我们测试这些想法在一个简单但现实的故障模型中存在的非线性率相关的摩擦。我们发现，如果摩擦力随着滑移率的降低而增加，则滑移在低滑移率下变得不稳定，产生超声愈合阶段，从而过早地锁定滑移。滑移的锁定反过来又产生应力不均匀性。对于包含单个局部粗糙体的断层模型，Das和Okubo发现破裂从粗糙体开始并传播，直到它遇到强大的障碍或应力强度降低到最低水平以下。在这些模型中，破裂完全由破裂前缘的物理性质控制。速率相关的摩擦以基本的方式改变了断层的行为：摩擦可以过早地锁定断层，从而产生超声愈合阶段。与障碍物产生的停止阶段不同，愈合阶段不是波动现象;它是摩擦非线性的直接结果。在这种情况下，断层上滑移的上升时间不再像传统的常摩擦裂纹模型那样由断层的整体尺寸控制。我们发现，在我们的粗糙模型，它是上升时间或愈合机制，控制故障的最终大小。研究模型涉及几个孤立的凸体，我们发现，应力的异质性被保存提供摩擦是强烈的速率相关。根据破裂过程的细节，断层上的最终应力状态可能相当复杂。这种行为不是普遍的，它取决于摩擦的速率依赖程度。
It has recently been proposed by several authors that stress distribution around active faults may become critical spontaneously. Other authors believe that heterogeneity is a permanent feature of fault planes. We test these ideas on a simple but realistic fault model in the presence of non-linear rate-dependent friction. We find that if friction increases with decreasing slip rate, slip becomes unstable at low slip rates generating supersonic healing phases that lock slip prematurely. Locking of slip in turn produces stress heterogeneity. For a fault model containing a single localized asperity, Das and Okubo found that rupture starts at the asperity and propagates until it either encounters a strong barrier or the stress intensity reduces below a minimum level. Rupture in these models is completely controlled by the physics of the rupture front. Rate dependent friction changes the behavior of the fault in a fundamental way: friction can lock the fault prematurely generating supersonic healing phases. Unlike stopping phases produced by barriers, a healing phase is not a wave phenomenon; it is a direct consequence of the non-linearity of friction. In this case rise time for slip on the fault is no longer controlled by the overall size of the fault as in conventional constant-friction crack models. We find that in our asperity models it is rise time or the healing mechanism that controls the final size of the fault. Studying models involving several isolated asperities we find that stress heterogeneity is preserved provided that friction is strongly rate dependent. Depending on the details of the rupture process, the final state of stress on the fault can be quite complex. This behavior is not universal, it depends on the degree of rate-dependence of friction.