Tectonic evolution of Savu
Islands are situated in a tectonic subduction
zone, where the Indo-Australian Plate is moving
northward, sliding under the Eurasian Plate. The
islands lie on a ridge that was created by
volcanic eruptions caused by the plate movement.
The Sumba Ridge is no longer volcanically active,
however there are active volcanos on the island
of Flores, to the north. Sediments carried into
the Earth's crust heat up and rise in plumes of
magma, which cool and solidify to form igneous
The compression of the two tectonic plates is
causing the Savu Islands to rise at a rate of
about 1mm per year. Occasionally, however, the
tectonic plate suddenly slips a much greater
distance, resulting in an earthquake. In 1977, a
major earthquake, registering 7.9 on the Richter
Scale (RS), struck 280km W/SW of Rai Jua. Since
1970, over 40 earthquakes greater than 6.0 RS
have struck within 500km of Savu. As can be seen
on the map, below, many
of these earthquakes were situated beneath the
sea, some shallow enough to cause tsunamis.
Earthquakes in East Nusa Tenggara
map in a separate frame
Copyright © 2006 Ina
Tali/Francesca Von Reinhaart
Geology of Indonesia
IAGI (Ikatan Ahli Geologi Indonesia - Indonesian
Association of Geologists).
De la Subduction Oceanique a la
Subduction Continentale Deformations Associees et
Heritage Structural: L'exemple du bloc
Sumba-Savu, terminaison orientale du fosse de la
These de Doctorat de l'Universite Pierre &
Hamson, G. (2004)
Tectonic Evolution of the Banda Orogen, East
Veritas Geophysical Services
Seismic data of the sea
bed surrounding Savu and Sumba.
M.W. & Harris, R.A.
Geology, B.Y.U, provo, UT 84602
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