Regional and semi-regional modelling of wide-angle shear waves in OBS data from the Vøring Basin, N. Norway—a comparison

Autor: Toshihiko Kanazawa, Shuichi Kodaira, Per Digranes, Hajime Shiobara, Rolf Mjelde, Hideki Shimamura
Rok vydání: 2003
Předmět:
Zdroj: Earth, Planets and Space. 55:65-81
ISSN: 1880-5981
DOI: 10.1186/bf03351734
Popis: Shear wave refractions and wide-angle reflections recorded on densely spaced Ocean Bottom Seismometers (OBSs) in the Voring Basin have been modelled by use of 2-D kinematic ray-tracing. Twenty-five three component OBSs were deployed along a 120 km long profile, and the semi-regional shear-wave velocity model derived from modelling the horizontal components is compared with a regional model from 5 OBSs along the same profile. The overall shear-wave velocity distribution of the two models are fairly similar, proving that the regional procedure with large OBS spacing provides a reliable regional shear-wave velocity model. The semi-regional model is more detailed than the regional model due to the much closer receiver spacing. The vertical resolution is improved, especially in the shallow sediments, and this enables a more detailed lithological interpretation to be carried out. Intermediate and deep sediments are also better resolved in the semi-regional model, indicating both vertical and lateral changes in the lithology. The V p /V s ratio inferred for the crystalline basement is 1.75 in both models, considered to be typical for the continental crust. An increase in the V p /V s ratio in the lower crust is observed both in the regional and in the semi-regional model. This indicates a more mafic composition in the lower crust, supporting the interpretation that the lower crust is a “mixing” of continental crust and magmatic underplating.
Databáze: OpenAIRE