Pulse-like ruptures induced by low-velocity fault zones
Pulse-like ruptures induced by low-velocity fault zones
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低速断层带引起的脉冲状破裂
DOI：
10.1029/2011jb008684
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发表时间：
2011
影响因子：
--
通讯作者：
J. Ampuero
中科院分区：
文献类型：
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作者：
Yihe Huang;J. Ampuero
低速断裂带（LVFZ）在大多数成熟断层中发现。它们通常为100-400 m宽，相对于围岩，波速降低约20%-60%。为了研究LVFZs对地震破裂和辐射波场的影响，我们进行了二维（2-D）模拟动态破裂的断层平分LVFZ，考虑一系列的速度减少和宽度。大多数地震的滑动上升时间显然比它们的总破裂持续时间短得多。一些动力学机制，这种脉冲状破裂已被提出，包括摩擦自愈，故障强度不均匀性，和双材料的影响。我们发现，破裂LVFZ足够强的波速对比表现为脉冲。这些脉冲由从LVFZ的边界反射的波引起的故障锁定产生。这种脉冲产生机制对初始应力、LVFZ结构的平滑度、断裂模式的变化以及摩擦愈合的排除是稳健的。此外，我们发现LVFZ可以产生复杂的破裂模式。低速降低的LVFZ诱导多个破裂前沿，涉及共存的脉冲和裂纹。具有一定宽度的LVFZ可以加速向超剪切破裂的转变。LVFZ对动态破裂的这些附加影响可以有助于高频地面运动的复杂性。
Low-velocity fault zones (LVFZs) are found in most mature faults. They are usually 100–400 m wide and have ~20%–60% wave velocity reductions relative to the country rock. To study the effect of LVFZs on earthquake rupture and the radiated wavefield, we conducted two-dimensional (2-D) simulations of dynamic rupture on faults that bisect a LVFZ, considering a range of velocity reductions and widths. Most earthquakes apparently have slip rise times much shorter than their overall rupture duration. A number of dynamic mechanisms for such pulse-like ruptures have been proposed, including frictional self-healing, fault strength heterogeneities, and bimaterial effects. We find that ruptures in LVFZs with strong enough wave velocity contrast behave as pulses. These pulses are generated by fault locking induced by waves reflected from the boundaries of the LVFZ. This mechanism of pulse generation is robust to variations of initial stress, smoothness of the LVFZ structure, rupture mode, and exclusion of frictional healing. Moreover, we find that LVFZs can generate complex rupture patterns. LVFZs with low-velocity reduction induce multiple rupture fronts involving coexisting pulses and cracks. LVFZs with certain widths can accelerate the transition to supershear rupture speed. These additional effects of LVFZs on dynamic rupture can contribute to the complexity of high-frequency ground motions.