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The North Andean Margin
Wednesday 2 November 2011 by Jean-Yves Collot

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The north Andean margin, from Ecuador to western Colombia, shows a structural segmentation that result from eastward subduction of the Nazca plate and Carnegie ridge at 5.4 cm/yr, and northeastward tectonic escape of the North Andean Block (Fig.1). _ This segmentation confers a remarkable earthquake history on the margin. Southern and central segments of the Ecuador margin are historically little or not affected by large subduction earthquakes, whereas the northern Ecuador segment and SW Colombia margin were struck by several devastating earthquakes and tsunamis during the 20th century. _ In 1906 the interplate fault ruptured over more than 500 km in length during a great, Mw 8.8 earthquake (Fig. 1). The rupture zone was reactivated from south to north by smaller magnitude events in 1942 (Mw 7.8), 1958 (Mw 7.7) and 1979 (Mw8.2), thus defining barriers between rupture zones and seismological asperities. _ In 2000, GEOMER initiated an onshore-offshore scientific research program to explore the seismogenic zone along the North Andean margin. _ _ Cruises - [SISTEUR->120] (N.O. NADIR and N.O. Orion, 2000) Crustal investigations of the Ecuador-Souther Colombia active margin using Multichannel Seismic Reflection and Wide-Angle Seismic (OBS=Ocean Bottom Sismometer). - [SALIERI->122] (N.O. SONNE, 2001) Crustal and seafloor Investigations of the Carnegie Ridge, and northern and southern segments of the Ecuador margin using Wide-Angle Seismic with a high-density of OBS and swath bathymetry. - [AMADEUS->124] (N.O. L’Atalante, 2005) Detailed morphology, submarine neotectonics, mass transfer deposits, thermal structure, sedimentary record of great subduction earthquakes along the North Ecuador-SW Colombia margin using sawth bathymetry, single-channel seismic, 3.5 kHz, coring, dredging and heat flow measurements. - [ESMERALDAS->125] (N.O. L’Atalante et N.O. Providencia 2005). 3D-active and passive local tomography, earthquake localization, seismotectonics and study of non-linear effects of the ground motion, using an onshore-offshore network of broadband seismometers and OBS on the active margin of Northern-Ecuador Southern Colombia. _ _ Participants _ J-Y Collot (DR-IRD), P. Charvis (DR-IRD), N. Bethoux (Mdc, UNS), B. Pontoise (DR-IRD), J-F Dumont (CR-IRD), Y. Font (CR-IRD), A. Galvey (CR-CNRS, F. Michaud (MdC, UPMC), S. Migeon (MdC, UNSA), S. Operto, (CR-CNRS), M. Régnier (CR-IRD), A. Ribodetti (CR-IRD), F. Sage (MdC UPMC), M. Sosson (CR-CNRS). _ _ Cooperations _ Avec l’Institut de Géophysique de l’EPN, l’INOCAR et Petroproduccion en Equateur, INGEOMINAS, DIMAR et l’Université EAFIT en Colombie, Geomar en Allemagne, le CSIC de Barcelone en Espagne et l’Université de Victoria et le Pacific Geosciences Center au Canada, Université de Bordeaux I, Université Antilles-Guyane. _

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