Supershear rupture of the 5 January 2013 Craig, Alaska (Mw 7.5) earthquake
Supershear rupture of the 5 January 2013 Craig, Alaska (Mw 7.5) earthquake
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DOI：
10.1002/2013jb010594
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发表时间：
2013-11
期刊：
影响因子：
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通讯作者：
H. Yue;T. Lay;J. Freymueller;K. Ding;L. Rivera;N. Ruppert;K. Koper
中科院分区：
文献类型：
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作者：
H. Yue;T. Lay;J. Freymueller;K. Ding;L. Rivera;N. Ruppert;K. Koper
超剪切破裂是指裂缝尖端的扩展速度超过弹性剪切波速度的一种破裂，已从理论和实验上进行了广泛的研究，并已从6次大陆走滑地震的地震波观测中推断出来。我们发现了2013年1月5日阿拉斯加克雷格7.5级大洋板间地震超剪切破裂扩展的广泛证据。这种不对称的双边走滑破裂发生在阿拉斯加东南部近海的夏洛特女王断层上。几个区域地震台站在距震源较近的断层上观测到的首波Sn和Sg剪切波，用经验格林函数方法提供的路径标定，表明了一个超剪切破裂过程。进一步应用多种波形反演和模拟技术，利用区域地震和大地测量资料，确定了破裂速度和滑动的时空分布。分析中使用了理论和经验的格林函数，所有结果都与破裂速度一致，破裂速度为5.5~6公里/S，超过了地壳和上地幔的S波速度，接近地壳P波速度。超剪破裂发生在断裂带北段约100公里处，而不是沿较短的南侧破裂延伸。超剪切破裂的发展方向可能与理论和实验预测的跨越大陆-海洋板块边界的强烈物质对比度有关。剪切马赫波和面波马赫波涉及在与破裂方向倾斜的方位角上强烈增强的地面运动，强调了大走滑地震的超剪切破裂所带来的增强的危险性。
Supershear rupture, in which a fracture's crack tip expansion velocity exceeds the elastic shear wave velocity, has been extensively investigated theoretically and experimentally and previously inferred from seismic wave observations for six continental strike‐slip earthquakes. We find extensive evidence of supershear rupture expansion of an oceanic interplate earthquake, the 5 January 2013 Mw = 7.5 Craig, Alaska earthquake. This asymmetric bilateral strike‐slip rupture occurred on the Queen Charlotte Fault, offshore of southeastern Alaska. Observations of first‐arriving Sn and Sg shear waves originating from positions on the fault closer than the hypocenter for several regional seismic stations, with path calibrations provided by an empirical Green's function approach, indicate a supershear rupture process. Several waveform inversion and modeling techniques were further applied to determine the rupture velocity and space‐time distribution of slip using regional seismic and geodetic observations. Both theoretical and empirical Green's functions were used in the analyses, with all results being consistent with a rupture velocity of 5.5 to 6 km/s, exceeding the crustal and upper mantle S wave velocity and approaching the crustal P wave velocity. Supershear rupture occurred along ~100 km of the northern portion of the rupture zone but not along the shorter southern rupture extension. The direction in which supershear rupture developed may be related to the strong material contrast across the continental‐oceanic plate boundary, as predicted theoretically and experimentally. The shear and surface wave Mach waves involve strongly enhanced ground motions at azimuths oblique to the rupture direction, emphasizing the enhanced hazard posed by supershear rupture of large strike‐slip earthquakes.