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Press release
Earthquake in Algeria: CNRS scientists on the job | |||
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Paris, June 2, 2003 |
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earthquake of May 21, 2003, along the coast of Algeria, mobilized the "Groupe
d’Intervention Post-Sismique" (Post-Seismic Intervention Group)
of the INSU/CNRS, of creating a multidisciplinary research team (seismology,
tectonics, marine geophysics, geodetics). The team is studying this earthquake
in order to better quantify seismic hazards(1) in the region
and to ultimately work with other organizations in order to better manage
seismic risks(2) such as the vulnerability of buildings,
for example. The scientific activities of about a dozen laboratories in
France are thus coordinated with their counterparts at the "Centre
de Recherche en Astrophysique, Astronomie et Géophysique" (Research
Center for Astrophysics, Astronomy and Geophysics) in Algiers, Algeria.
Researchers from the Humanities and Social Sciences Department of the CNRS
will also be involved in the project, which may bring together up to thirty
French researchers. Seismic stations were immediately set up in Algeria to register the aftershocks of the main earthquake. "Marine" stations will be installed on the ocean floor in the very near future. Geodesic stations have been registering ground deformation on a continual basis for several days now. Spatial imaging is being used to quantify co-seismic deformation (RADAR images) and damage (high resolution optical images). Finally, a marine geophysical campaign that had already been planned for this region for August 2003, in partnership with IFREMER, will provide detailed images of the sea floor and the rupture, in order to verify the hypothesis of underwater landslides. This Algerian earthquake was felt on the other side of the Mediterranean, in France, Spain and in Italy. A tsunami was observed in the Balearic Islands and along the French coast and many telecommunication cables laid on the sea floor were carried away. This was a major earthquake for the western Mediterranean, of a magnitude of 6.7, comparable to the Campania (Italy) earthquake in 1980 and the El Asnam (Algeria) earthquake in October 1980. Seismic activity along the Algerian coast is not new. It is the result of the collision between the African and European continents, caused by plate tectonics. These two continents are converging on each other at a speed of approximately several mm/year. A small part of the resulting deformation can be seen in Europe where it contributes to the creation of mountain chains (the Alps and the Pyrenees). The rest (the biggest part) is distributed along a fault system, partially on the land and partially under the sea, running along the African "margin". This slow deformation gradually builds up near the faults that are generally inhibited by their "roughness". The sudden rupture of the fault eases the deformation accumulated over the centuries. Initial calculations show that the earthquake of May 21 is typical of earthquakes in this region. It took place on a very oblique fault surface with a total upward displacement of several meters between the two blocks. The energy released by the earthquake was concentrated in the southwestern direction (towards Alger), partially explaining the major damage that occurred in this area.
Department
of Sciences of the Universe contact: |
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