HR: 0830h
AN: S41D-0119    [PDF]
TI: Modal Depth Analysis of the Oceanic Lithospheric Bending Along the Chilean Margin, from a new Detailed Bathymetric Synthesis
AU: * Clouard, V
EM: valerie@dgf.uchile.cl
AF: Dept de Geofisica - U. de Chile, Blanco Encalada 2085, Santiago, 2777 Chile
AU: Vera, E
EM: evera@dgf.uchile.cl
AF: Dept de Geofisica - U. de Chile, Blanco Encalada 2085, Santiago, 2777 Chile
AB: The Chilean margin has been the focus of numerous study investigating the subduction style of the Nazca plate under South America. We present an analysis of the bending of the oceanic lithosphere from north to south, based on an original bathymetric compilation. Our bathymetric database includes 169 cruises with satellite navigation, digitalized bathymetric map contours from Nazca Project and bathymetric prediction grid (version 8.2) of Sandwell and Smith (1997). After crossover analysis of the single beam sonar data, only 124 cruises are kept. Prediction data are used to fill gaps where no other data are available. Our final 250m resolution grid presents a smooth transition between high and low resolution bathymetry. The resulting grid is used to characterize the bending of the lithosphere prior to subduction. From 17S to 44S, segments of 1 degree wide in latitude are extracted. Only those with high resolution data are kept to carry out a modal analysis, where depth is given as a function of distance to the trench. For each segment, the mode depth/distance contour map provides the geometrical characteristics of the bending: The amplitude of the bending along the Chilean Margin ranges from 850m at 20S, to only 25m near 26S and 36S. We built universal flexure profiles that best fit the maxima of the modes. The elastic thickness (Te) of the lithosphere is directly computed from each profile. The obtained Te for each segment is compared with the one corresponding to the age of the lithosphere. Large variations exist, which mainly correlate with the transition from flat slab to normal subduction. In this zone, an increased by more than 50% to a decreased by half elastic thickness occurs in only 2 degrees of latitude from north to south.
DE: 3045 Seafloor morphology and bottom photography
DE: 7218 Lithosphere and upper mantle
DE: 7220 Oceanic crust
DE: 9360 South America
SC: Seismology [S]
MN: 2003 Fall Meeting