Source discriminants for near-field tsunamis
Source discriminants for near-field tsunamis
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DOI：
10.1111/j.1365-246x.2004.02347.x
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发表时间：
2004-07
影响因子：
2.8
通讯作者：
E. Okal;C. Synolakis
中科院分区：
文献类型：
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作者：
E. Okal;C. Synolakis
摘要我们提出了一个数据集的72个模型的源，涉及地震位错和滑坡的海啸助跑在近场的数值模拟。通过逐一改变描述源和接收海滩的参数，我们能够分离它们对助跑的幅度和分布的单独影响，我们通过形成几个无量纲参数来表征助跑，主要是其最大幅度与其沿着海滩的横向范围的比率I2。我们发现，对于地震位错源，I2仍然小于10 −4，但对于所有物理上真实的水下滑坡模型，I2都大于这个阈值。因此，它可以被用来作为一个判别近场海啸的源的性质。对于地震位错，我们还考虑了比I 1的最大助跑地震滑动的断层面上，并验证数值以前建议的“经验法则”，这个比例不能远大于1。在水下滑坡的情况下，我们表明，近场助跑的分布主要是由2-D的“墙的水”在海洋表面上作为初始条件的模拟位移控制，实际上是独立于其在第三个维度的延伸，垂直于海滩。我们采用这种方法，以九个配置文件的海啸助跑实验获得在最近的实地调查，并表明，我们的方法成功地确定了1998年巴布亚新几内亚海啸已产生的水下滑坡，从而证实了船上和水声调查的结果。这也强烈地表明了1946年4月1日近场阿留申海啸的产生机制类似。
SUMMARY We present numerical simulations of tsunami run-up in the near field for a data set of 72 models of sources, involving both seismic dislocations and landslides. By varying one by one the parameters describing the source and the receiving beach, we are able to separate their individual influence on the amplitude and distribution of run-up, which we characterize by forming several dimensionless parameters, principally the ratio I 2 of its maximum amplitude to its lateral extent along the beach. We find that I 2 remains less than 10 −4 for seismic dislocation sources but is greater than this threshold for all physically realistic models of underwater landslides. Thus, it can be used as a discriminant for the nature of the source of a near-field tsunami. For seismic dislocations, we also consider the ratio I 1 of maximum run-up to seismic slip on the fault plane, and validate numerically the previously suggested ‘rule of thumb’ that this ratio cannot be much greater than 1. In the case of underwater landslides, we show that the distribution of near-field run-up is primarily controlled by the 2-D ‘wall of water’ displaced on the ocean surface as an initial condition to the simulation, and is practically independent of its extension in the third dimension, perpendicular to the beach. We apply this approach to nine profiles of tsunami run-up obtained experimentally during recent field surveys, and show that our method successfully identifies the 1998 Papua New Guinea tsunami as having been generated by an underwater landslide, thus confirming the results of shipboard and hydroacoustic investigations. It also strongly suggests a similar mechanism for the generation of the near-field Aleutian tsunami of 1946 April 1.