TSUNAMI OF THE SUMBA EARTHQUAKE OF AUGUST 19,1977
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A large earthquake of normal type with a magnitude (M_w) of 8.3 occurred off the southwest coast of Sumba Island, Indonesia at 14h 08m local time (06h 08m GMT) on August 19,1977. It caused a large tsunami which struck the south coasts of Bali, Lombok, Sumbawa, and Sumba Islands. Tsunami heights were 5-8 meters at Lunyuk on Sumbawa Island, and 5 meters at Leterua on the south coast of Sumba Island. Hatori's tsunami magnitude was estimated as m=3.5 from data on the tsunami heights at 15 points on the Indonesian and Australian coasts. Numbers of casualties and missing persons respectively were 107,and 54,and most were victims of the tsunami. We made a numerical calculation of tsunami propagation by assuming two sets of fault parameters. The simulation showed that the tsunami height distribution was well reproduced numerically for the larger dislocation in the western part of the fault plane than in the eastern part. After the main shock, loud noises that sounded like explosions were heard three times at several points northwest of the epicenter. Similar noises were heard during the 1933 Great Sanriku Earthquake-Tsunami, also a normal type event. We speculate that such noises are peculiar to normal type earthquakes.