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Le Projet Spiral Enjeux et Questionnements en risques naturels

Le Projet Spiral Enjeux et Questionnements en risques naturels. Yelles AbdelKarim Spiral Team. E4°. E3°. N37°. SISMICITE MARINE. Boumerdes , 2003. Djidjelli 1856. Bathymetrie , 1955. Principaux séismes (1365-2006). 03.02.1716 M=7.5 20000 Morts. 03.01.1365 Io=X.

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Le Projet Spiral Enjeux et Questionnements en risques naturels

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  1. Le Projet SpiralEnjeux et Questionnements en risques naturels Yelles AbdelKarim Spiral Team

  2. E4° E3° N37° SISMICITE MARINE Boumerdes, 2003 Djidjelli 1856 Bathymetrie, 1955

  3. Principaux séismes (1365-2006) 03.02.1716 M=7.5 20000 Morts 03.01.1365 Io=X 21.05.2003 M=6.8 2300 Morts 10.11.2000 M=5.4 2 Morts 04.09.1996 M=5.7 02.08.1856 M=7.5 Plusieurs Morts 29.10.1989 M=6.0 22 Morts 15.01.1891 M=7.5 38 Morts 27.10.1985 M=6.0 300 Blessés 09.03.1858 M=6.5 09.09.1954 M=6.7 1234 Morts 20.03.2006 M=5.8 09.10.1790 M=7.5 2000 Morts 24.06.1910 M=6.6 81 Morts 02.01.1867 M=7.5 100 Morts 12.02.1946 M=5.6 264 Morts 18.08.1994 M=5.6 172 Morts 16.11.1869 M=6.5 30 Morts 02.03.1825 M=7.5 7000 Morts 22.12.1999 M=5.8 28 Morts 10.10.1980 M=7.3 2633 Morts 21.02.1960 M=5.6 47 Morts 29.11.1887 M=7.5 22 Morts 02.04.2006 M=5.4

  4. Earthquake-relateddeformation : Historicalseismicity • « Discontinuous coverage » • « Deficient record » Benouar, 2001 Boughacha et al., 2004 1716–1910 and 1911-2000: 2430 events, 4 « seismogenicsub-regions », A Intensity map (before the 2003 event) • Offshore seismicityknownsince 3 centuries at least, but poorlyestimated • « Coastal » earthquakes (< 100 km fromcoastline) are the strongest and best documented • 1350-1950: only 6 eventswith IX and more (6.5 < M < 7.5): • Algiers 02.01.1365 Probable tsunami • Algiers 03.02.1716 20 000 killed • Oran 09.10.1790 3000 killed • Blida 02.03 1825 7000 killed • Jijel 22.08.1856 tsunami • Gouraya 15.01.1891 40 killed tsunami poorlydocumented Sources poorlyconstrained, except 1856 (Jijel)

  5. El Asnam Fault zone • 9 events M > 7 before 1980, over ~7 kyrs • 5 wellestablished (d) • 4 uncertain (p) Paleoscarps Uplifted terraces Sediment flows Meghraoui et al., 1988 C. Authemayou, personal comm.2010 -> Repeatedcoseismicdisplacements -> Minimum uplift rate : 0.6 mm/yr (average) -> M > 7 return period: 350-500 yr (« cluster » periods) 1000-1800 yr (« quiet » periods) Meghraoui et al., 1988

  6. 1 Slow convergence, Tethyan suture (Miocene), complex & spread deformation Kinematicand seismo-geological background Eurasia 1.6±0.6 mm/yr 8 mm/yr 4 mm/yr 1901-2004 3.9 ±0.9 mm/yr Africa Serpelloni et al., 2007 Suture Internal-External zones Flyshs ->A SEA-LAND APPROACH REQUIRED ! Domzig et al., 2006

  7. MARADJA2003, 2005 (SAMRA), PRISME2007 MDJ2005 MDJ2003 + PRISME 2007 MARADJA (MARge Active DJAzaïr) 2003-2005 +

  8. 3- Active faults and folds activity recognition Boumerdès fault : surface breaks ? 1 2 B1 B B2 B3 Mahsas et al., GJI, 2008 Prolongation of rupture towards the surface ? • Emergence 1: unlikely • Emergence 2: unlikely (except East) • Emergences B2-B3: likely -> Flat-ramp

  9. Résultats Maradja (2003-2005) Thèse Domzig, 2006 Yelles et al., 2009 • ~22 large active faults • Discontinuous distribution, overlaps • Southerndips, nearOcean-Continent Boundary, blindthrusts • Interpretation: Compressionalreactivation of the margin on bothsides of Internal Zones • apparent pop-up structure

  10. 1- Région d’Oran Domzig et al., 2006

  11. 2-Région Alger Yelles et al.,2009

  12. Réseau Sismologique

  13. A possible approach by segment boundaries 6- Conclusions and Perspectives T1 T2 T3 T4 T5 T6 T7 T8 T9 Holocene B M ~7-7.5 2003 D ? A M>7.3 1365, 1716, 1891, 1954, 1980 Multiple sources RP: 700yrs C M ~7-7.5 1856 Plot of core dating off Boumerdes (hemipelagic deposits (PSM-KS23 core) against El Asnam dating T0 (lost?) Boumerdes 2003 M ~7? PSM-KS23 Tentative comparisonbetween segments A - B T2? T1? : before Boumerdes? T3 T4? T5? Test of triggering /clustering between segments ? T6? T7 T8 MTD 8 7

  14. Projet SPIRAL Questionnements et enjeux en RISQUE SISMIQUE • - Géométrie des failles majeures (Relation entre failles profondes et failles actives). • - Connaissance des limites de blocs • Estimation taux de convergence (déformation) • Modèle de vitesse (meilleure localisation des séismes) • Connaissance des mécanismes de déformation (modèles de rupture…) • Modèle de zone de subduction naissante, limite de plaques (zonation sismique) • Evaluation de l’aléa sismique-tsunamigènique et gravitaire • - Réduction du risque sismique

  15. Enjeux Spiral ?

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