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  Tsunamis and the Savu Islands

Situated within an earthquake prone region and surrounded by sea, Savu and Rai Jua are exposed to tsunamis on all sides. Savu's coastline stretches 90km and its coastal plains cover an area of approx. 30 sq.km. Thousands of people live near, or work on the coast, such as fishermen, seaweed farmers and salt producers. The most vulnerable communities are the villages of Heb’a, Menia and B’od’ae, where the coastal plains are broadest. The area depicted as light green on the map below could be inundated by a large tsunami, since it lies below the 12.5m contour.

A major tsunami could inundate the coastal plain.

This happened in 1977, when a major earthquake, registering 7.9 on the Richter Scale (RS), struck 280km W/SW of Rai Jua (see map below). This triggered an enormous tsunami, which swept across the coastal plain at Seba, reaching as high as the airport (see map above). No one was reported missing on Savu or Rai Jua. However, on the neighbouring islands of Sumba and Sumbawa, the death toll reached 180.

Earthquakes in East Nusa Tenggara 1970-2004
Enlarge map in a separate frame
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Since 1970, 10 earthquakes with magnitudes greater than or equal to 6.0 RS have struck beneath the Savu Sea. In 1995, an earthquake registering 6.9 RS struck midway between the island of Alor and East Timor. The resulting tsunami flooded an area 120m inland and caused the disappearance of 11 people. However, the Indian Ocean poses a far greater threat, since major earthquakes are concentrated along the plate boundary, situated 150km to the south of Savu. This is the junction of the colliding Indo-Australian and Eurasian Tectonic Plates.

Since 1900, 212 earthquakes with magnitudes greater than or equal to 7.0 RS have occurred along this tectonic subduction zone, which extends from north Sumatra to east of Timor. Eighty five percent of these quakes (183) were located beneath the sea, with forty seven percent of these (86 submarine quakes) generating tsunamis-on average one every 14 months. The proximity of their epicentres to the coast ranges from 0 to 300 km, so the resulting tsunamis typically hit land within 30 minutes of the quake.

Copyright © 2006 Ina Tali/Francesca Von Reinhaart

© raijua.com

References:

Hamson, Gillian (2004)
The Tectonic Evolution of East Timor and the Banda Arc
Honours Literature Review submitted as part of the B.Sc.(Hons) degree in the School of Earth Sciences,
University of Melbourne

NOAA's National Geophysical Data Center (NGDC)

Pararas-Carayannis, G. (1977)
Indonesian Earthquake and Tsunami of August 19, 1977.
Abstracted article in
Tsunami Newsletter, Vol. X, No. 3. (Sept. 1977). (1.8MB .pdf).
International Tsunami Information Center Report.


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