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yexuqing木虫之王 (文学泰斗)
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停止相揭示大型走滑地震的突然止裂
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Stopping phase reveals abrupt arrest of large strike-slip earthquakes 停止相揭示大型走滑地震的突然止裂 ▲ 作者：JESSE KEARSE AND YOSHIHIRO KANEKO ▲链接： https://www.science.org/doi/10.1126/science.aef3733 ▲摘要： 地震震级受控于破裂传播在何处、何时停止。然而，在天然地震的近场地震记录中，破裂止裂现象很少被直接观测到。研究者展示了大型走滑地震中地面运动停止相的系统性近场观测结果。对全球12次地震事件的分析表明，平行断层方向的地表位移中的瞬态过冲是破裂传播突然终止的可靠诊断标志。 动态破裂模拟显示，浅层低波速岩石会强烈放大近场地动信号，从而增强地表记录到的位移过冲幅度。停止相出现在远离已知破裂末端的近断层位置，这意味着大型走滑地震以分段方式破裂，动态破裂传播在内部断层段边界处会被突然中止并重新启动。 ▲ Abstract： Earthquake magnitude is controlled by where and when rupture propagation stops. However, rupture arrest has rarely been directly observed in near-field seismic records of natural earthquakes. Here, we present systematic near-field observations of ground-motion stopping phases from large strike-slip earthquakes. Analysis of 12 global events shows that transient overshoot in fault-parallel ground surface displacement is a robust diagnostic signature of abrupt termination of rupture propagation. Dynamic rupture simulations reveal that near-field ground motions are strongly amplified by low-wavespeed rocks at shallow depth, which enhances the amplitude of displacement overshoot recorded at the surface. The occurrence of stopping phases at near-fault locations far from mapped rupture termini implies that large strike-slip earthquakes rupture in a segmented manner, with dynamic rupture propagation punctuated by abrupt arrest and reinitiation at internal fault-segment boundaries. |
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