Hideo Matsutomi

Damage, conditions of East Java Tsunami of 1994 analyzed

On June 3, 1994, an Ms = 7.2 earthquake occured at a depth of 15 km near the east end of the Java trench in the Indian Ocean. The earthquake generated a large tsunami that violently struck southeast Java and extended to southwest Bali (Figures 1 and 2). Approximately 200 people were killed, 400 were injured, and 1000 houses were destroyed. Runup heights (Figure 2) ranged from 0–5 m in west Bali to 1–14 m in southeast Java. n nThis unusual tsunami was generated about 250 km from the hardest hit area. Surprisingly, strong earthquake-induced ground shaking was not a precursor so local residents had no warning of the impending catastrophe. The long-period characteristics of the earthquake were incommensurate with the relatively weak high-frequency magnitude Mb=5.5, and the rate of seismic moment release grew monotonically up to at least 270s. The pattern resembled that of the Nicaragua earthquake of September 2, 1992, in which strong ground shaking did not occur. Most of the damage was concentrated in villages located in pocket beaches, unlike previous tsunami damage in west Nicaragua, Flores, Indonesia [Yeh et al., 1993], and Okushiri, Japan.

Irian Jaya earthquake and tsunami cause serious damage

On February 17,1996, at 0559 UT, a major earthquake with moment magnitude (Mw) 7.9 killed 107 people and caused major damage at Biak Island, 30–40 km southwest of the earthquakes epicenter (Figures 1 and 2). A devastating tsunami washed away all of the houses at Korim, a small village located in a narrow bay facing directly towards the incoming wave, and it left behind clear evidence of sand erosion and deposition that indicated how far the tsunami advanced. An unexpectedly large tsunami run-up of 7.7 m was measured at Wardo in western Biak, which faces away from the primary tsunami source. This high run-up may have been caused by a local submarine landslide.

Response of Residents at the Moment of Tsunamis-The 1992 Flores Island Earthquake Tsunami, Indonesia-

The number of loss of lives due to the 1992 Flores island tsunamis was about 1,000. The maximum tsunami runup height 26.2m was measured at Kroko. At Babi island, reflected tsunami with the height of 5 to 7m attached two villages so that every structure was broken and swept away. At Waring, mooring fishing boats were easily carried to the dense-housing areas by tsunamis so that wooden-made houses were swept away by dominos. Through the questionnaire, tsunami characteristics and residents’ behavior are also described. Most residents have no information on tsunamis. After looking at tsunami coming, they run away to safe places. Therefore, the disaster weak such as children and old people might fell victim to the tsunami disaster. As disaster lessons, spread of tsunami information such as local tsunami characteristics and refuge programs are very important to mitigate the damages in tsunami-prone areas.

THE MEASURED AND COMPUTED HOKKAIDO NANSEI-OKI EARTHQUAKE TSUNAMI OF 1993

A special reflecting wall 12 m long and 2.1 m high was built off the beach at Reggio Calabria, and 30 wave gauges were assembled before the wall and were connected to an electronic station on land. It was possible to observe the reflection of wind waves generated by a very stable wind over a fetch of 10 Km. The experiment aimed to verify the general closed solution for the wave group mechanics (Boccotti, 1988, 1989), for the special case of the wave reflection.Significant features on Wadden Sea wave climate are evaluated in respect of the state of the art. Main emphasis was laid on an analysis of the governing boundary conditions of local wave climate in island sheltered Wadden Sea areas with extensions being sufficient for local wind wave growth. Explanatory for significant wave heights a reliable parametrization of local wave climate has been evaluated by using generally available data of water level and wind measurements.