Role of Bathymetry in Tsunami Simulations
Ling-Wan Liao
Abstract
In order to understand more about tsunamis, numerical simulation is an important method of research. By simulating tsunamis, researchers can not only reproduce the observed tsunamis, but also estimate unobserved tsunami heights.
To make the simulation model closer to real situations, many papers are founded on improving models to consider about more and more factors. There are three significant factors that affect the simulation: the governing equations (linear and nonlinear shallow water equations), bottom frictional values, andthe grid size of bathymetry data. There are two examples to proof the role of bathymetry in tsunami simulations.
¢¹. 1992 Nicaragua Earthquake Tsunami:
The earthquake (Ms=7.4) occurred at 00 h 15 m 57.5 s on September 2 (GMT). After about thirty minutes, two tidal gauge stations recorded the abnormal heights and field survey measured the runup height soon.The maximum runup height was 9.9 m above the mean sea level, but the runup heights are mostly between 3 and 8 m along the coast. The observations compare with the simulation resultsusing different governing equations, bottom frictions and bathymetry data shows that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms.
¢º. 1998 Papua New Guinea Tsunami:
On July 17, 1998, an earthquake (Ms=7.1) occurred near Sissano lagoon, Papua New Guinea at 8 h 49 m 13.2 s (GMT) cause very large tsunami, more than 10 m height. The large tsunami heights and damage were limited in approximately 30 km section of the coast near the mouth of Sissano Lagoon. To explain the localize nature of the event, a submarine landslide has been conjectured to be responsible. But simulating with newly obtained bathymetry may also explain the concentrated tsunami. Although the definitive cause of the Papua New Guinea tsunami remains uncertain, local bathymetry had a notable effect on the wave behavior.
Reference
SATAKE, K. (1995), Linear and Non-linear Computations of the 1992 Nicaragua Earthquake Tsunamis. Pure Appl. Geophys, Vol. 144, 455-470.
Matsuyama, M., Walsh, J.P., and Yeh, H. (1999) The effect of bathymetry on tsunami characteristics at Sissano Lagoon, Papua New Guinea. Geophysical ResearchLetters, Vol. 26, 3513-3516.
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