A closing Ligurian Sea? |
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| Authors: | N Bethoux J Fréchet F Guyoton F Thouvenot M Cattaneo C Eva M Nicolas M Granet |
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| Institution: | (1) CSM, Musée océanographique, Monaco;(2) Present address: Institut de Géodynamique, URA 1279, CNRS, Avenue A. Einstein, 06560 Valbonne, France;(3) LGIT, Observatoire de Grenoble, IRIGM, BP 53X, 38041 Grenoble Cedex, France;(4) IGG, Dipartemento di Scienze della Terra, viale Benedetto XV, 5, 16132 Genova, Italy;(5) LDG/CEA, BP 12, 91680 Bruyères-le-Chatel, France;(6) EOPGS, 5 rue René-Descartes, 67084 Strasbourg Cedex, France |
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| Abstract: | Two earthquakes occurred in the Ligurian Sea in December 1989 and April 1990. Both were widely felt along the French and Italian Rivieras, thus reminding us of the seismic risk in this region. The significant increase in the number of seismic stations in the area facilitated the study of these two shocks and their related aftershocks. Using different techniques (absolute and relative hypocentral locations, doublet analysis and waveform modeling), we computed accurate hypocentral locations and estimated the location-error range for earthquakes in this area. We also computed the focal mechanisms for both mainshocks, and we present here a synthesis that integrates previous data. The reactivation in compression of the Ligurian Sea sphenochasm is confirmed, which would eventually result in the closing of an aborted oceanic domain. As the seismic activity is clearly restricted to the northern margin, we suggest it locally results from the lateral expulsion of the south-western Alps along the Apulian indenter. |
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| Keywords: | Earthquakes aftershocks spatial distribution Ligurian Sea seismicity |
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