Tectonic evolution of Savu

The 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 rock.

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 1970-2004
Enlarge map in a separate frame
(Flash Player required).

Copyright © 2006 Ina Tali/Francesca Von Reinhaart



The Geology of Indonesia
IAGI (Ikatan Ahli Geologi Indonesia - Indonesian Association of Geologists).

Fleury, Jean-Marc
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 Sonde.
These de Doctorat de l'Universite Pierre & Marie Curie

Hamson, G. (2004)
The Tectonic Evolution of the Banda Orogen, East Timor.

Veritas Geophysical Services
Seismic data of the sea bed surrounding Savu and Sumba.

Vorkink, M.W. & Harris, R.A.
Geology, B.Y.U, provo, UT 84602
Geoscience in a changing world

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