The Role of Frontal Thrusts in Tsunami Earthquake Generation
The Role of Frontal Thrusts in Tsunami Earthquake Generation
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DOI：
10.1785/0120210154
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发表时间：
2022-04-01
影响因子：
3
通讯作者：
Switzer, Adam D.
中科院分区：
文献类型：
--
作者：
Felix, Raquel P.;Hubbard, Judith A.;Switzer, Adam D.
俯冲带的前缘部分是一种鲜为人知的危险的来源：“海啸地震”，由于地震震动，它产生的海啸比预期的要大。在这些地震中，前缘逆冲断层上的滑动被认为是波高增加的原因，但这种机制的影响迄今尚未量化。在这里，我们探讨如何正面逆冲滑动可以有助于海啸波的产生，通过模拟所产生的海底变形断层弯曲褶皱理论。然后，我们量化的波高在2D和预期的海啸能量在3D的逆冲splays（使用断层弯曲折叠）和下倾滑脱破裂（模拟为弹性）。我们提出了一个解析解的水柱的阻尼效应，并表明，由于锋面逆冲滑动产生的海底隆起的窄带阻尼，初始海啸的高度和由此产生的能量是相对较低的。虽然冲断层的几何形状可以改变海底变形，但水阻尼减少了这些差异;海啸能量通常对冲断层斜坡参数（如断层倾角、地质演化、沉积和侵蚀）不敏感。海啸能量主要取决于三个特征：海底下的滑脱深度、水深和同震滑动。由于俯冲带的前缘断裂包括前缘逆冲断层和下倾滑脱断层的滑动，我们比较了它们的海啸能量。我们发现，逆冲斜坡产生的能量显着低于对滑脱滑移。使用2010年10月25日M-w 7.8明打威海啸地震的案例研究，我们表明，虽然滑脱和锋面推力一起可以产生所需的海啸能量，
The frontal sections of subduction zones are the source of a poorly understood hazard: "tsunami earthquakes," which generate larger-than-expected tsunamis given their seismic shaking. Slip on frontal thrusts is considered to be the cause of increased wave heights in these earthquakes, but the impact of this mechanism has thus far not been quantified. Here, we explore how frontal thrust slip can contribute to tsunami wave generation by modeling the resulting seafloor deformation using fault-bend folding theory. We then quantify wave heights in 2D and expected tsunami energies in 3D for both thrust splays (using fault-bend folding) and down-dip decollement ruptures (modeled as elastic). We present an analytical solution for the damping effect of the water column and show that, because the narrow band of seafloor uplift produced by frontal thrust slip is damped, initial tsunami heights and resulting energies are relatively low. Although the geometry of the thrust can modify seafloor deformation, water damping reduces these differences; tsunami energy is generally insensitive to thrust ramp parameters, such as fault dip, geological evolution, sedimentation, and erosion. Tsunami energy depends primarily on three features: decollement depth below the seafloor, water depth, and coseismic slip. Because frontal ruptures of subduction zones include slip on both the frontal thrust and the down-dip decollement, we compare their tsunami energies. We find that thrust ramps generate significantly lower energies than the paired slip on the decollement. Using a case study of the 25 October 2010 M-w 7.8 Mentawai tsunami earthquake, we show that although slip on the decollement and frontal thrust together can generate the required tsunami energy,