HR: 0800h
AN: T11A-0358    [Abstracts]
TI: Sub-seafloor Structures and Heat Flow Measurements at the Ecuador-Colombia Subduction Margin: Preliminary Results From the R.V. L'Atalante AMADEUS Cruise.
AU: * Collot, J
EM: collot@geoazur.obs-vlfr.fr
AF: G‚osciences-Azur, BP48, Villefranche sur Mer, 06235 France
AU: Alvarado, A
EM:
AF: IG-EPN, Ladr¢n de Guevara, Quito, 17-01-2759 Ecuador
AU: Dumont, J
EM:
AF: G‚osciences-Azur, BP48, Villefranche sur Mer, 06235 France
AU: Eissen, J
EM:
AF: IRD-LMV, Rue Kessler, Clermont-Ferrand, 63038 France
AU: Joanne, C
EM:
AF: G‚osciences-Azur, BP48, Villefranche sur Mer, 06235 France
AU: Lebrun, J
EM:
AF: Univ. Antilles-Guyane, BP 592, Pointe … Pitre, 97159 France
AU: Legonidec, Y
EM:
AF: G‚osciences-Azur, BP48, Villefranche sur Mer, 06235 France
AU: Lewis, T
EM:
AF: PGC, PO6000, Sidney, V8L4B2 Canada
AU: Lopez-Ramos, E
EM:
AF: Ingeominas, Dg53 Nø34-53, Bogota, 1 Colombia
AU: Marcaillou, B
EM:
AF: G‚osciences-Azur, BP48, Villefranche sur Mer, 06235 France
AU: Martinez, I
EM:
AF: Univ. EAFIT, AA3300, Medellin, 1 Colombia
AU: Michaud, F
EM:
AF: G‚osciences-Azur, BP48, Villefranche sur Mer, 06235 France
AU: Migeon, S
EM:
AF: G‚osciences-Azur, BP48, Villefranche sur Mer, 06235 France
AU: Oggian, G
EM:
AF: Univ. Bordeaux I, Av. des Facult‚s, Bordeaux, 33405 France
AU: Pazmino, A
EM:
AF: INOCAR, Via Puerto Maritimo, Guayaquil, 1 Ecuador
AU: Santana, E
EM:
AF: INOCAR, Via Puerto Maritimo, Guayaquil, 1 Ecuador
AU: Schneider, J
EM:
AF: Univ. Bordeaux I, Av. des Facult‚s, Bordeaux, 33405 France
AU: Sosson, M
EM:
AF: G‚osciences-Azur, BP48, Villefranche sur Mer, 06235 France
AU: Spence, G
EM:
AF: Univ. of Victoria, VSW3P6, Victoria, 1 Canada
AU: Toro, A
EM:
AF: Ingeominas, Dg53 Nø34-53, Bogota, 1 Colombia
AU: Wada, I
EM:
AF: PGC, PO6000, Sidney, V8L4B2 Canada
AB: The N-Ecuador and SW-Colombia margin underwent great (7.7 <Mw <8.8) subduction earthquakes in 1906, 1942, 1958 and 1979. Previous MCS and OBS investigations have provided information on the plate interface and clues for a margin transverse segmentation that closely matches earthquake rupture zones. In February-Mach 2005, the AMADEUS cruise collected 55000 km2 of contiguous swath bathymetry coverage and underway geophysics, 21 sedimentary cores, 920 kg of rocks dredged at 14 sites, and heat flow data at 12 core and heat probe sites. The cruise objectives were to investigate -the 3D geometry and tectonic history of crustal faults associated with the seismogenic plate interface, -major routes for terrestrial sediments, avalanche masses and debris flows, -the recurrence time of subduction earthquakes through their sedimentary records, -and temperatures at the locked plate interface. Preliminary results reveal a spectacular 330 km-long submarine canyon-channel system and associated 3.5-km-thick, deep-sea turbidite system derived from the Esmeraldas and Patia-Mira river systems. Based on morphology and sediment nature, erosional processes and sediment transport appear to be more active in the Esmeraldas canyon than in the Patia-Mira canyon. Numerous 5-10-km-wide scars associated with debris toes and locally with subducting seamounts point to margin slope instabilities. Abundant creeping and slide structures were discovered along the fore-arc basin flanks, where numerous, headless gullies might be related to gas or fluid seeps. Narrow reflective stripes, perpendicular to gullies, may reflect co-seismic liquefaction structures. A near-bottom, semi-transparent echo-facies was observed in the fore-arc basin and trench, suggesting water-rich layers, possibly liquefied and homogenized by seafloor acceleration during earthquakes. The new bathymetric map supports the margin segmentation. It shows a tectonic contrast between an uplifting, margin-wide, fold-and-thrust belt associated with the 1979 earthquake rupture zone north of ~1°50'N, and a wide, subsident fore-arc basin, which correlates with 1958 rupture zone. Furthermore, the newly discovered NW-trending fault that cuts through an outer basement high, and the NE-trending fault separating the basement high from the fore-arc basin correlate with northward and seaward limits of the 1958 rupture zone suggesting that the fault activity may reflect tectonics of the seismogenic zone. Thermal modeling constrained by BSR-derived heat flow have indicated that along-strike heat flow variations matches the margin structural segmentation. Seafloor heat probe measurements, obtained seaward of the deformation front, average 94.7 mW/m2 and 121 mW/m2 in the north of the survey, 65.2 and 54 mW/m2 in the center, and 55.9 mW/m2 in the south in relatively good agreement with BSR-derived heat flow. Two 5-km-long heat flow profiles at a spacing of 200-250m were collected along MCS lines where BSR-derived heat flow indicated large localized variations. Heat probe values were less than the BSR-derived values by ~10 mW/m2, but the overall trends agreed well.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 3070 Submarine landslides
SC: Tectonophysics [T]
MN: Fall Meeting 2005