Resultados de la estructura cortical en el margen catalán (NE de la Península Ibérica) a partir de la sísmica profunda de reflexión y refracción


  • N. VIDAL


The crustal structure at the NE Iberian Peninsula and the transition to the Mediterranean is investigated from recent geophysical data based on reflection and refraction seismics. A crustal transect on land, from the Pyrenees to the Mediterranean coast is available after the Spanish steep reflection ESCI profile. Its continuation at sea, across the Valencia trough up to the south Balearic basin is currently under treatment. A complete processing sequence was applied to de ESCIland line. This included crooked-line geometry, trace editing, static corrections, CMP sorting, dynarnic corrections, residual statics, stacking, poststack time variant bandpass filtering, energy balance, time and depth migration, and semblance/coherency filtering. The crustal seismic image documents the sedimentary sequence in the Cenozoic and Neogene basins, and differentiates an almost transparent upper crust from a highly reflective lower crust below 13-14 km depth. The reflector a re deeping northwards beneath the Ebro basin and become sub-horizontal across the Catalanides. The Moho is located at about 32 km depth. In the Reus basin, due to the sedimentary thickness, the continuity of internal structures must be solved using complementary wide-angle and refraction data. High-quality recordings up to 50 km inland of the air-gun shots from the marine ESCI profile provide a complementary image of the strncture on land. The lateral variability is investigated using a second profile displaced 30 km to the northeast. The two parallel lines with a high-density of measurements constrain the velocity-depth distribution and reveal a crustal thinning towards the Valencia trough. One third of the crustal thickness is lost in a range of 60 km distance. The crust remains of continental type according to the velocities deduced, and the thinning happens mainly in the lower crust.

A number of results along the coast line indicate that the Moho is affected by lateral short-wavelength variations, which can be associated with the horst and graben structuration of the Catalan margin produced by the Neogene extensional tectonics.