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
(Flash
Player required).
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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