The crustal structure of the southern Rhinegraben from re-interpretation of seismic refraction data
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Vols. 1-18 (1924-1944), ISSN 0044-2801
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Abstract
The Rhinegraben is one of the best studied rift structures in the world. In the past 20 years, it has been the site of many seismic refraction studies. However, most of the profiles have only been interpreted using 1-D methods. In this paper a combined 2-D and 1-D analysis of the only reversed profile within the graben proper is presented. The new interpretation has resulted in changes in the P-wave velocity model of the Rhinegraben. In the new model, the upper crust of the graben, representing the sedimentary graben-fill, is found to be 6-7 km thick with Vp less than 6.0 km/s. The mid-crust, which is probably of granitic/gneissic composition, shows a practically constant velocity of 6.25 km/s. This observation is supported by seismic reflection data. At the base of the crust is a velocity discontinuity followed by a 1.5 km thick transition zone into the upper mantle. From north to south along the graben, the crust thins by 3 km and the upper mantle velocity changes from about 8.4 km/s to 7.9 km/s. In comparison with the old 1-D model, the new model shows a simplification of the structure of the lower crust and a thinning of the crust/mantle transition zone from 5 km to 1.5 km. Furthermore, in the old model, the upper mantle velocity underneath the graben was found to be constant at 8.1 km/s, which is in contrast to the changing upper mantle velocity found in the new model.
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References
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