Deep seismic reflection profiling in the Swiss Alps: Explosion seismology results for line NFP 20-East

Abstract

In September 1986, a 120-km-long seismic line was recorded through the Swiss Alps. The line traverses major units involved in thin- and thick-skinned Alpine tectonics. Our preliminary interpretation indicates that (1) lithologic boundaries such as basement-cover contacts, although severely deformed during the Alpine orogeny, can be identified on the seismic sections; (2) the top of the Aar massif, an external basement massif, extends deep into the Alpine orogen; (3) the upper and lower parts of the crust are more or less transparent, but are separated by a swarm of reflectors at mid-crustal level; (4) these mid-crustal reflectors might be related to trapped fluids from Alpine metamorphism; and (5) the Moho appears as a bright reflection that steepens from the north toward the south and terminates abruptly near the center of the Alpine chain, perhaps because of Alpine deformation.