Crustal structure of the Northern tip of the Antartic Peninsula from wide-angle and normal incidence seismic data

DELLA VEDOVA, B.; ACCAINO, F.; CERNOBORI, L.; PELLIS, G.; PETRONIO, L.; RINALDI, C.; ROMANELLI, M.; TASSONE A.

Barcelona

Seminario; 8th International Symposium on Deep Seismic Profiling of the Continents and their margins; 1998

EUG

The Hero FZ intercepts nearly orthogonal the Pacific margin of the Antarctic Peninsula (AP) at about 63° S; it separates a progressively older and older passive margin, to the SW, from an active subduction with associated back-arc extension (Bransfield Strait) to the NE. During the austral summer 1996-97, a joint Italy-Argentina geophysical study (TENAP project) was carried out across the northern tip of the AP, on either sides of the Hero FZ, to reconstruct the crustal structure and the deformation processes in the area. The measurements undertaken include active source and passive seismology, gravity, total magnetic field and geology investigations. Three near vertical reflection seismic profiles (about 700 km in total) were acquired on the Pacific side of the AP, using a 3 km long multichannel streamer and a 60.5 litres air gun array, operated in "single bubble" mode, shooting every 50 m. A second passage was performed along the same lines, shooting . into OBS and land stations only, with a 250 m interval. The energy was recorded by digital ocean-bottom seismographs deployed in 16 positions along the lines and by 15 portable seismic stations deployed on the AP, up to a source-receiver distance of 240 km. Preliminary models from the active source seismic measurements indicate a crustal thickness of about 40 km for the AP cordillera and a crustal structure of its pacific margin differing significantly across the Hero FZ: a back­stop characterised by rifting, block faulting and Moho depths of 16-18 km beneath Bransfield St., to the NE, contrasts with a passive margin where the Moho depth is about 25 km, to the SW.