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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Redistribution of dynamic stress during coseismic ruptures: Evidence for fault interaction and earthquake triggering
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Redistribution of dynamic stress during coseismic ruptures: Evidence for fault interaction and earthquake triggering

机译：同震破裂过程中动应力的重新分布：断层相互作用和地震触发的证据

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摘要

We investigate the spatiotemporal evolution of dynamic stress outside a rupturing extended fault. The dynamic stress variations caused by a coseismic rupture in a half space are computed by using the discrete wavenumber and reflectivity methods. After a transient phase, the stress time history evolves to the final static stress value. We compare the static stress changes resulting from this model with those computed from a static dislocation model. We have applied this method to study the interactions between the first two normal faults which ruptured during the 1980 (M_S 6.9) Irpinia earthquake. These two subevents are separated in time by nearly 20 s, while the third (and last) subevent occurred 40 s after the rupture onset. We compute the dynamic stress changes caused by the rupture of the first subevent. Our modeling results show that the dynamic stress peak on the second subevent fault plane is reached between 7 s and 8 s after the rupture initiation on the main fault. On the average the static stress level on the second subevent (20 s) fault plane is reached nearly after 14 s. The dynamic rupture did not jump from a rupturing segment to the adjacent one immediately, but the triggering of the 20 s subevent is delayed by roughly 10 s with respect to the instant of occurrence of the dynamic stress peak induced by the 0 s event. The dynamic stress pulse propagates along the strike direction of the second subevent fault plane at an average velocity of nearly 3.4 km/s. The delayed triggering of the second subevent can be interpreted in terms of the frictional properties of the faults. In particular, rate- and state-dependent frictional law can explain a delayed instability after a sudden change in stress. Using the estimated values of the subevent triggering delay and the shear stress change, we attempt to constrain the parameter A#sigma# on the 20 s fault. The values here inferred agree well with those resulting from previous studies.
机译：我们调查了断裂扩展断裂外的动态应力的时空演化。使用离散波数和反射率方法计算了半空间内同震破裂引起的动应力变化。在过渡阶段之后，应力时间历程演变为最终的静态应力值。我们将由该模型产生的静态应力变化与从静态位错模型计算出的静应力变化进行比较。我们已应用此方法研究了1980年（M_S 6.9）Irpinia地震中破裂的前两个正断层之间的相互作用。这两个子事件在时间上相隔将近20 s，而第三个（也是最后一个）子事件发生在破裂开始后40 s。我们计算由第一个子事件的破裂引起的动态应力变化。我们的模拟结果表明，在主断层开始破裂后，第二个子事件断层平面上的动应力峰值达到了7 s和8 s之间。平均而言，几乎在14 s后，第二个子事件（20 s）断层平面上的静应力水平就达到了。动态断裂并未立即从断裂段跳到相邻的断裂段，但是相对于由0s事件引起的动态应力峰值的发生时刻，20s子事件的触发被延迟了大约10s。动应力脉冲以接近3.4 km / s的平均速度沿第二子事件断层平面的走向传播。可以根据故障的摩擦特性来解释第二子事件的延迟触发。特别地，速率和状态相关的摩擦定律可以解释应力突然变化后延迟的不稳定性。使用子事件触发延迟和剪切应力变化的估计值，我们尝试将参数A＃sigma＃约束在20 s故障上。此处推断的值与先前研究得出的值非常吻合。

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