TSUNAMI SOURCES IN THE SUMATRA REGION, INDONESIA AND SIMULATION OF THE 26 DECEMBER 2004 ACEH TSUNAMI

A total of 19 tsunamis generated by earthquakes occurred in the Sumatra region in the period from 1770 to 2005. About 84 % of the tsunamigenic earthquakes have magnitude Ms> 6.0 and about 86 % of them have focal depth less than 100 km. This characteristic is comparable with the characteristics of tsunamigenic earthquakes in the Pacific region. The empirical relationship between tsunami intensity I on Soloview-Imamura scale and the earthquake magnitude Ms can be written as I = 0.80Ms – 4.18. The tsunamigenic earthquakes in the Sumatra region tend to generate larger tsunami than the ones in the Pacific region where the relationship can be written as I = 1.22Ms – 8.89. A numerical tsunami simulation was performed to model the 26 December 2004 Aceh tsunami by utilizing a method developed by the Tohoku University. In general, the calculated tsunami arrival times were comparable with the observed or reported ones, while the calculated tsunami heights were smaller than the observed ones. Judging from the root-mean-square error values at Sibolga and Belawan tide gauge stations it can be noted that the amplitude of the time series of the calculated tsunami heights were quite different compared to the observed ones. However, their coefficient correlation values were relatively high which may indicate that the shape of the two time series of the calculated tsunami heights were comparable with the observed ones