Enregistrements sédimentaires imbriqués d'une activité sismique et de changements paléoenvironnementaux. Etude de différents sites : Golfe de Corinthe (Grèce), Lac de Shkodra (Albanie/Monténégro) et Golfe de Cariaco (Vénézuela).

Abstract : Since several tens of years, the assessment of local to regional seismic hazard – mainly based on seismology and tectonic analysis – is reinforced by paleoseismic data yielded by recent sedimentary archives. The later ones may be (paleo-)lakes as well as closed marine basins, developed close to, or upon, main active faults. These sediments are investigated on outcrops or on cores, and, when possible, in parallel with high resolution seismic imagery interpretation. Based on the expertise acquired by the LGCA on the Sea of Marmara (North-Anatolian Fault) and on the South-Caribbean Plate boundary (Boconó Fault), the present work aimed to: 1) Bring a methodological contribution to the assessment of earthquake-related deposits, 2) separate the paleo-environmental information (climate, human impact) from the paleoseismic ones, 3) contribute to the understanding of tectono-sedimentary systems on a regional scale. Two main sites have been elected along the Egean Arc: the Corinth Gulf (Greece) and the Shkodra Lake (Albania/Montenegro boundary). A preliminary high resolution seismic reflection survey of the Cariaco Gulf (north-eastern Venezuela) is added. The two sites were chosen in order to compare two sedimentary accumulations undergoing similar historical seismicity (close to 7 in magnitude, 2 to 3 major events per century), but very different with respect to depositional depth, sedimentary processes, and accumulation rates. The records are lasting respectively 20 kyr (Corinth) and 10 kyr (Shkodra) back from Present. Beside studies aiming to characterize the evolution of nature and texture of the sediment composition, the use of magnetic properties, in particular Anisotropy of Magnetic Susceptibility, was developed. This approach enabled to characterise changes of depositional processes and reworking phenomena (turbidites, homogenites). Our results reinforce the usefulness of this tool while assessing more precise conditions for its use. For each site, the search of sedimentary traces of historical earthquakes preceded the possible extrapolation of the results back to longer periods. The Shkodra site (very shallow) did not yield significant paleoseismic archive, but well a marked climatic signal since more than 7000 years. For the Corinth site, the frequency of layers possibly related to earthquakes is compatible with regional historical data and show enhanced exportation in the depth by mass wasting during the lacustrine phase. Eustatic fluctuations effect on sedimentation were also identified. The Cariaco site displays few co-seismic disturbances visible at seismic imagery scale. Nevertheless, our results enabled to define faults systems present in the Gulf and also propose a very first chronological framework for the sedimentation.
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Applied geology. Université de Savoie, 2007. French


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Submitted on : Friday, March 7, 2008 - 4:08:17 PM
Last modification on : Friday, March 7, 2008 - 4:37:30 PM

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  • HAL Id : tel-00261605, version 1

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INSU | LGCA | OSUG | GIP-BE | UGA

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Aurelien Van Welden. Enregistrements sédimentaires imbriqués d'une activité sismique et de changements paléoenvironnementaux. Etude de différents sites : Golfe de Corinthe (Grèce), Lac de Shkodra (Albanie/Monténégro) et Golfe de Cariaco (Vénézuela).. Applied geology. Université de Savoie, 2007. French. <tel-00261605>

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