Using a dynamic earthquake simulator to explore tsunami earthquake generation
Using a dynamic earthquake simulator to explore tsunami earthquake generation
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使用动态地震模拟器探索海啸地震的产生
DOI：
10.1093/gji/ggab470
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发表时间：
2021
影响因子：
2.8
通讯作者：
Luo, Bin
中科院分区：
文献类型：
--
作者：
Meng, Qingjun;Duan, Benchun;Luo, Bin
对历史海啸地震的观测表明，这类地震的破裂在浅部传播缓慢，持续时间较长，高频辐射损耗较大，Mw-Ms值的差异较大。它们可以有效地产生海啸，并对沿海地区的人口稠密地区造成巨大破坏。在这项研究中，我们使用一个最近开发的动态地震模拟器，探讨海啸地震的生成从物理为基础的建模的角度来看。我们建立了一个浅倾俯冲带模型，其中局部锁定，不稳定的补丁（凸）分布在一个条件稳定的俯冲界面在浅深度。动态地震模拟器捕捉地震周期的准静态和动态过程。我们发现，地震可以在这些凹凸体上成核，并以低速传播到周围的条件稳定区，产生海啸地震。一个高的正应力凹凸体，代表一个俯冲海山，可以作为一个凹凸体在某些事件中，但作为一个障碍，在其他事件在多个地震周期。在海啸地震中，低法向应力粗糙体通常起着粗糙体的作用。条件稳定区中的速度弱化程度是海啸地震发生的关键，它可能维持不同速度的破裂或停止破裂，并影响海啸地震的复发间隔。分布的粗糙体可能在相隔数十年的孤立事件中破裂，或在相隔数小时至数天的事件序列中破裂，或在级联方式的一个大事件中破裂，表明它们之间的复杂相互作用。高正应力微凸体上的复发间隔比低正应力微凸体上的复发间隔大得多。这些模拟结果揭示了历史海啸地震的观测结果，包括1994年和2006年的爪哇海啸地震和2010年的明打威海啸地震。
Observations of historical tsunami earthquakes reveal that ruptures of these earthquakes propagate slowly at shallow depth with longer duration, depletion in high-frequency radiation and larger discrepancy ofMw–Msthan ordinary megathrust earthquakes. They can effectively generate tsunami and lead to huge damage to regional populated areas near the coast. In this study, we use a recently developed dynamic earthquake simulator to explore tsunami earthquake generation from a physics-based modelling point of view. We build a shallow-dipping subduction zone model in which locally locked, unstable patches (asperities) are distributed on a conditionally stable subduction interface at shallow depth. The dynamic earthquake simulator captures both quasi-static and dynamic processes of earthquake cycles. We find that earthquakes can nucleate on these asperities and propagate into the surrounding conditionally stable zone at slow speeds, generating tsunami earthquakes. A high normal stress asperity, representing a subducted seamount, can act as an asperity in some events but as a barrier in other events over multiple earthquake cycles. Low normal stress asperities typically act as asperities in tsunami earthquakes. The degree of velocity-weakening in the conditionally stable zone, which may sustain rupture at different speeds or stop rupture, is critical for tsunami earthquake generation and affects its recurrence interval. Distributed asperities may rupture in isolated events separated by tens of years, or in a sequence of events separated by hours to days, or in one large event in a cascade fashion, demonstrating complex interactions among them. The recurrence interval on a high normal stress asperity is much larger than that on low normal stress asperities. These modelling results shed lights on the observations from historical tsunami earthquakes, including the 1994 and 2006 Java tsunami earthquakes and 2010 Mentawai tsunami earthquake.