Deterministic chaos in a simulated sequence of slip events on a single isolated asperity
Deterministic chaos in a simulated sequence of slip events on a single isolated asperity
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单个孤立粗糙体上滑动事件模拟序列中的确定性混沌
DOI：
10.1093/gji/ggu157
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发表时间：
2014
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影响因子：
--
通讯作者：
N
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文献类型：
--
作者：
Kato;N
利用断层块(凹凸体)上滑动事件反复发生的数值模拟，解释了滑动事件序列不规则的机制。断层是恒定速率的均匀剪切载荷，作用在断层上的摩擦应力服从与速率和状态有关的摩擦(RSF)定律。断层中埋藏着一块具有减速摩擦性的圆形斑块，除此之外，它还具有增速摩擦性。采用RSF定律的各种特征滑移距离进行了数值模拟。对于较小的L值，滑动事件(地震)以规则的间隔重复发生。随着l的增大，滑移事件的重现变得更加复杂。一种双周期滑动模式，其中地震和非地震滑动事件交替发生，出现多周期和非周期模式。同时，滑移有随L增大而变得抗震的趋势。由于前一次滑动事件的残余应力和地震间隔期的无震滑动产生的剪应力的变化，断层在滑动事件之前的剪应力分布是不同的。剪切应力的这些变化导致了这里所看到的复杂的滑动事件序列。对于滑动事件的非周期序列，滑动事件的重现间隔的迭代映射被表示为一条简单的曲线，表明事件的定时可以从先前的时间间隔中预测，并且滑动事件序列呈现确定性混沌。为了帮助解释嵌入在速度增强区中的速度弱化块上的一系列滑移事件的结果，对被永久锁定区域包围的速度弱化块上的滑移进行了数值模拟。在这种情况下，没有观察到滑动事件的复杂重现。当LhenL值小于临界值时，地震滑动事件以恒定的间隔重复发生。当L值大于临界值时，发生稳定滑动。这一结果表明，嵌入在速度增强区中的速度弱化斑块的复杂滑移行为是由速度弱化区和速度增强区之间的相互作用引起的。
Numerical simulation of repeated occurrences of slip events on a fault patch (asperity) is used to interpret the mechanism of irregular sequences of slip events. The fault is uniformly shear loaded at a constant rate, and the frictional stress acting on the fault is assumed to obey a rate- and state-dependent friction (RSF) law. A circular patch with velocity-weakening frictional property is embedded in the fault, which apart from this has velocity-strengthening frictional property. The numerical simulations are conducted using various characteristic slip distancesLof the RSF law. For small values ofLseismic slip events (earthquakes) repeatedly occur at regular intervals. With increasingL, the recurrence of slip events becomes more complex. A period doubled slip pattern, where seismic and aseismic slip events alternately occur, multiperiodic patterns and aperiodic patterns occur. At the same time, slip tends to become aseismic with increasingL. The distributions of shear stress on the fault just before slip events are variable because of variation in the residual stress of the preceding slip event and the shear stress generated by aseismic sliding during interseismic periods. These variations in shear stress cause the complex sequence of slip events seen here. An iteration map of the recurrence intervals of slip events for an aperiodic sequence of slip events is expressed by a simple curve, indicating that the timing of an event is predictable from the previous time interval, and the sequence of slip events exhibits deterministic chaos. To help interpret these results for a sequence of slip events on a velocity-weakening patch embedded in a velocity-strengthening region, a numerical simulation is conducted of slip on a velocity-weakening patch enclosed by a permanently locked region. In this case, no complex recurrence of slip events is observed. WhenLis less than a critical value, seismic slip events repeatedly occur at a constant interval. Stable sliding occurs whenLis larger than the critical value. This result indicates that the complex slip behaviour seen for a velocity-weakening patch embedded in a velocity-strengthening region is caused by the interaction between the velocity-weakening and velocity-strengthening regions.