Details

Autor(en) / Beteiligte

• Ansorge, J
• Holliger, K
• Valasek, P
• Ye, S
• Finckh, P
• Frei, W
• Kissling, E
• Lehner, P
• Maurer, H
• Mueller, St
• Smithson, S. B
• StäUble, M
• Meissner, Rolf
• Brown, Larry
• Franke, Wolfgang
• Seifert, Friedrich
• Dürbaum, Hans‐Jürgen
• Fuchs, Karl

Titel

Integrated Analysis of Seismic Normal Incidence and Wide‐Angle Reflection Measurements Across the Eastern Swiss Alps

Ist Teil von

• Continental Lithosphere: Deep Seismic Reflections, 1991, p.195-205

Ort / Verlag

Washington, D. C: American Geophysical Union

Erscheinungsjahr

1991

Quelle

Wiley Online Library All Obooks

Beschreibungen/Notizen

• Deep crustal seismic data extending along a N‐S transect through the eastern Swiss Alps have been compiled to form a detailed image of the crustal structure across a portion of this continental collision zone. The data sample the entire Alpine edifice beginning in the Molasse Basin in the north and ending in the Po Plain. The image incorporates both large‐scale refraction and wide‐angle reflection measurements as well as near‐vertical deep‐crustal reflection profiles. The reflection surveys are part of the Swiss National Science Foundation Program NFP‐20 and are almost coincident with the Alpine segment of the European Geotraverse (EGT). Examples of the two types of data are displayed separately and then combined as a single composite section. The EGT wide‐angle reflection data are shown also as NMO‐corrected profiles. The standard, reduced traveltime sections were used to select seismic events to base forward modeling by 2D raytracing. The NMO‐corrected wide‐angle data reproduce the sections in a normal‐incidence format which can be compared directly to the deep‐crustal reflection profiles. The reflection data from several of the NFP‐20 traverses are compiled after migration in a line‐drawing format onto a single transect. These migrated reflection data are superimposed on the crustal velocity structure obtained from refraction modeling which includes generalized velocity information from profiles crossing the EGT. Most of the main structural seismic features correlate well between the reflection and refraction data sets. In particular, a remarkable agreement exists between the reflection and refraction Mohos. From the refraction data the base of the European crust is shown to dip from 35 km depth in the north to 56 km beneath the Penninic nappes. A 18 km thick slab of lower crust is subducted further south under the Southern Alps. On the reflection data, this interface correlates well with the base of a 3–6 km thick package of deep reflections which suggests a transitional velocity‐depth distribution. Steeply dipping structures such as the Insubric line are less well imaged on the reflection profile which crosses it, but are clearly visible on the more distant high‐resolution reflection spreads. Overall, the advantage of this integration is a unified data base whereby the large‐scale velocity distribution derived from the refraction measurements is resolved in fine structural details by the reflection data.