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首页> 外文期刊>Pure and Applied Geophysics >Combined Effects of Tectonic and Landslide-Generated Tsunami Runup at Seward, Alaska During the M W 9.2 1964 Earthquake
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Combined Effects of Tectonic and Landslide-Generated Tsunami Runup at Seward, Alaska During the M W 9.2 1964 Earthquake

机译：1964年9.2级地震在阿拉斯加苏厄德构造和滑坡产生的海啸爆发的联合影响

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摘要

We apply a recently developed and validated numerical model of tsunami propagation and runup to study the inundation of Resurrection Bay and the town of Seward by the 1964 Alaska tsunami. Seward was hit by both tectonic and landslide-generated tsunami waves during the $M_{rm W}$ 9.2 1964 megathrust earthquake. The earthquake triggered a series of submarine mass failures around the fjord, which resulted in landsliding of part of the coastline into the water, along with the loss of the port facilities. These submarine mass failures generated local waves in the bay within 5 min of the beginning of strong ground motion. Recent studies estimate the total volume of underwater slide material that moved in Resurrection Bay to be about 211 million m3 (Haeussler et al. in Submarine mass movements and their consequences, pp 269–278, 2007). The first tectonic tsunami wave arrived in Resurrection Bay about 30 min after the main shock and was about the same height as the local landslide-generated waves. Our previous numerical study, which focused only on the local landslide-generated waves in Resurrection Bay, demonstrated that they were produced by a number of different slope failures, and estimated relative contributions of different submarine slide complexes into tsunami amplitudes (Suleimani et al. in Pure Appl Geophys 166:131–152, 2009). This work extends the previous study by calculating tsunami inundation in Resurrection Bay caused by the combined impact of landslide-generated waves and the tectonic tsunami, and comparing the composite inundation area with observations. To simulate landslide tsunami runup in Seward, we use a viscous slide model of Jiang and LeBlond (J Phys Oceanogr 24(3):559–572, 1994) coupled with nonlinear shallow water equations. The input data set includes a high resolution multibeam bathymetry and LIDAR topography grid of Resurrection Bay, and an initial thickness of slide material based on pre- and post-earthquake bathymetry difference maps. For simulation of tectonic tsunami runup, we derive the 1964 coseismic deformations from detailed slip distribution in the rupture area, and use them as an initial condition for propagation of the tectonic tsunami. The numerical model employs nonlinear shallow water equations formulated for depth-averaged water fluxes, and calculates a temporal position of the shoreline using a free-surface moving boundary algorithm. We find that the calculated tsunami runup in Seward caused first by local submarine landslide-generated waves, and later by a tectonic tsunami, is in good agreement with observations of the inundation zone. The analysis of inundation caused by two different tsunami sources improves our understanding of their relative contributions, and supports tsunami risk mitigation in south-central Alaska. The record of the 1964 earthquake, tsunami, and submarine landslides, combined with the high-resolution topography and bathymetry of Resurrection Bay make it an ideal location for studying tectonic tsunamis in coastal regions susceptible to underwater landslides.
机译：我们应用最近开发并经过验证的海啸传播和暴发数值模型来研究1964年阿拉斯加海啸对复活湾和苏厄德镇的淹没。在1964年9.2美元的特大推力地震中，苏厄德受到了构造波和滑坡产生的海啸的袭击。地震在峡湾周围引发了一系列海底大规模故障，导致部分海岸线滑坡入水，并失去了港口设施。这些海底质量故障在强烈地面运动开始后的5分钟内在海湾中产生了局部波浪。最近的研究估计，在复活湾中移动的水下滑道材料的总量约为2.11亿立方米（Haeussler等人，《海底大规模运动及其后果》，第269-278页，2007年）。第一次地震海啸在主震发生后约30分钟到达复活湾，其高度与当地滑坡产生的海浪相同。我们之前的数值研究仅关注复活湾的局部滑坡产生的波浪，结果表明它们是由许多不同的边坡破坏产生的，并估计了不同海底滑动复合体对海啸振幅的相对贡献（Suleimani等，2003）。 Pure Appl Geophys 166：131-152，2009年）。这项工作扩展了先前的研究，通过计算由滑坡产生的波浪和构造海啸的共同影响造成的复活湾海啸淹没，并将复合淹没面积与观测值进行比较。为了模拟苏厄德的滑坡海啸暴发，我们使用了江和勒布朗的粘性滑坡模型（J Phys Oceanogr 24（3）：559–572，1994），并结合了非线性浅水方程。输入数据集包括复活湾的高分辨率多波束测深法和LIDAR地形图网格，以及基于地震前后测深法差异图的滑动材料初始厚度。为了模拟构造海啸爆发，我们根据破裂区域的详细滑动分布推导了1964年的同震变形，并将其作为构造海啸传播的初始条件。该数值模型采用为深度平均水通量公式化的非线性浅水方程，并使用自由表面移动边界算法来计算海岸线的时间位置。我们发现，计算出的苏厄德海啸暴发首先是由当地海底滑坡产生的波，然后是构造海啸，与淹没区的观测结果非常吻合。对两种不同海啸源造成的洪水泛滥进行的分析有助于我们了解它们的相对贡献，并支持减轻阿拉斯加中南部的海啸风险。 1964年地震，海啸和海底滑坡的记录，再加上复活湾的高分辨率地形和水深，使其成为研究易受水下滑坡影响的沿海地区海啸构造的理想场所。

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