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Crustal structure and reflectivity of the Swiss Alps from three‐dimensional seismic modeling: 1. Helvetic Nappes
Author(s) -
Stäuble M.,
Pfiffner O. A.,
Smithson S. B.
Publication year - 1993
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/93tc00378
Subject(s) - geology , nappe , seismology , outcrop , massif , anticline , fold (higher order function) , fault (geology) , geomorphology , tectonics , paleontology , mechanical engineering , engineering
Forward modeling based on combined geologic surface data, borehole and laboratory data on velocities, and seismic reflection data aid in understanding the seismic response in a transect through complex Alpine nappe structures. The synthetic seismic response from the model compares well with the observed data. The results suggest, however, that strong three‐dimensional effects result in out‐of‐plane reflections and diffractions, as well as defocussing and scattering of seismic rays, thus rendering the use of two‐dimensional migration techniques questionable. The model shows an unexpected rapid change in internal structure of the Helvetic nappes between the seismic line and outcrops located 6–8 km farther west. Moreover, the basement‐cover interface on the northern flank of the Aar Massif, a basement uplift with a heave of 8 km, does not rise regularly in the hanging wall of a single major thrust fault, but rises in a series of steps due to several thrusts and folds. The northernmost structures appear to be fault‐related open folds, whereas tight fold structures appear to dominate in the south.