Abstract We analyze the ground motions of supershear ruptures in the Burridge-Andrews (BAM) and free-surface-induced (FSI) mechanisms. BAM supershear ruptures require higher initial shear stress than FSI supershear ruptures, thus cause faster rupture speed. The supershear slip pulse initiates at the free surface or upper boundary of a fault for FSI and at the hypocenter depth in the in-plane direction for BAM in homogeneous models. Both BAM and FSI supershear ruptures can generate Mach waves and the Rayleigh wave field. The BAM and the faster FSI supershear ruptures can make stronger shear Mach waves. The shear Mach waves show a larger amplitude of negative component for a faster FSI supershear rupture. The FSI supershear ruptures make the strongest dilatational wave next to the fault while it is at a distance away from the fault for the BAM supershear ruptures. The different shapes of supershear rupture front, locations of supershear triggered and the rupture speeds contribute to these contrasts. And we find that the BAM and the faster FSI supershear ruptures can trigger more high-frequency radiation due to the sharper and stronger shear Mach waves. Finally, the comparisons between the simulated seismograms and the records of PS10 indicate that the 2002 Denali earthquake may represent a supershear one with the FSI mechanism and a slow supershear rupture speed.

中文翻译：

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Burridge-Andrews 超剪切破裂的地面运动特征和自由表面诱发机制

摘要 我们分析了 Burridge-Andrews (BAM) 和自由表面诱导 (FSI) 机制中超剪切破裂的地面运动。BAM 超剪切断裂比 FSI 超剪切断裂需要更高的初始剪切应力，从而导致更快的断裂速度。超剪切滑动脉冲起始于 FSI 断层的自由表面或上边界，以及均质模型中 BAM 平面内方向的震源深度。BAM 和 FSI 超剪切破裂都可以产生马赫波和瑞利波场。BAM 和更快的 FSI 超剪切破裂可以产生更强的剪切马赫波。对于更快的 FSI 超剪切破裂，剪切马赫波显示出更大幅度的负分量。FSI 超剪切破裂在断层附近产生最强的膨胀波，而它与 BAM 超剪切破裂的断层相距一段距离。超剪切破裂前缘的不同形状、触发的超剪切位置和破裂速度导致了这些对比。我们发现 BAM 和更快的 FSI 超剪切破裂由于更尖锐和更强的剪切马赫波可以触发更多的高频辐射。最后，模拟地震图与 PS10 记录的比较表明，2002 年德纳利地震可能代表了具有 FSI 机制和缓慢超剪切破裂速度的超剪切地震。我们发现 BAM 和更快的 FSI 超剪切破裂由于更尖锐和更强的剪切马赫波可以触发更多的高频辐射。最后，模拟地震图与 PS10 记录的比较表明，2002 年德纳利地震可能代表了具有 FSI 机制和缓慢超剪切破裂速度的超剪切地震。我们发现 BAM 和更快的 FSI 超剪切破裂由于更尖锐和更强的剪切马赫波可以触发更多的高频辐射。最后，模拟地震图与 PS10 记录的比较表明，2002 年德纳利地震可能代表了具有 FSI 机制和缓慢超剪切破裂速度的超剪切地震。