Crustal structure along the Central Segment of the EGT from seismic-refraction studies

B. Aichroth, C. Prodehl*, H. Thybo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

113 Citations (Scopus)

Abstract

The seismic-refraction line between the Gulf of Genova and the Baltic Sea was carried out in 1986 as part of the European Geotraverse (EGT'86). The Central segment of the EGT, also known as EUGEMI (EUropean GEotraverse Middle part), has a total length of 825 km and runs from the northern margin of the Alps to the Baltic Sea, traversing mainly the Variscan mountain area of western Germany. The P-wave data of nine shotpoints were interpreted in detail and a two-dimensional P-velocity model of the crust was developed between the Molasse Basin and the southern end of the North German Basin. For the North German Basin the data quality justifies only the construction of a simplified model. The internal crustal structure is quite complex. In the upper crust of the Moldanubian and Saxothuringian zones of the Variscan orogen the velocities are lower than in the Rhenohercynian area. The velocity of 6.0 km/s, representing consolidated seismic basement, is reached at depths of as much as 10-12 km (northern margin of Alps and North German Basin) and of only 3 km under the Mid-German Crystalline Rise. Mid-crustal velocities range from 5.8 to 6.1 km/s, forming weak velocity reversals in some parts. In the lower crust velocities as low as 6.2 km/s are seen near the Alps, in contrast to velocities between 6.8 and 7.2 km/s in the exposed Variscan orogen north of shotpoint E. Between Hannover and the river Elbe the velocity of the lower crust is about 6.4 km/s, north of the Elbe Line it increases abruptly to 6.9 km/s. The crust-mantle boundary rises from 34 km depth under the northern margin of the Alps to 29 km under the Swabian Jura. Under the Variscan orogen to the north the crustal thickness varies only slightly around an average depth of about 29 ± 1 k, but drops to about 30 km under the North German Basin. Between the Elbe Line and the Ringkobing-Fyn High the Moho rises to a depth of about 26 km and the data indicate at least one fault-like step of 1 km before the crust thickens toward the basement high. The velocities in the uppermost mantle show considerable variation. The highest velocity of 8.4 km/s is observed beneath the Saxothuringian zone and the lowest values of 7.8-7.9 km/s are recorded under the Hessen depression.

Original languageEnglish
Pages (from-to)43-64
Number of pages22
JournalTectonophysics
Volume207
Issue number1-2
DOIs
Publication statusPublished - 30 Jun 1992
Externally publishedYes

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