Geophys. J. R. astr. SOC. zyxwvutsrq (1987), zyxwvut 89, 333-338 Combined seismic reflection and refraction profiling in southwest Germany - detailed velocity mapping by the refraction survey zy D. Gajewski, W.S. Holbrook and C. Prodehl Geophysical Summary. Within the framework of site survey studies of the Deep Drilling Program of the Federal Republic of Germany (KTB), coincident deep-seismic reflection and refraction experiments in the Black Forest, southwest Germany, were carried out. The simultaneous interpretation of the reflection and the refraction data reveals in particular both a strong velocity reduction in the upper crust and a laterally varying laminated structure of the lower crust. Additional refraction lines result in a three-dimensional crustal model which shows two distinct crustal types of different seismic properties. These crustal types seem to correlate with the major geologic units of Southwest Germany. Variations of Poisson's ratio derived from clearly recorded shear wave data show a similar trend. Institute, University zyxwvut of Karlsruhe, Herfzstr. zyxwvu 16,0-7500 Karlsruhe 21, zyxwv FR. Germany 1. Introduction In the framework of multi-disciplinary investigations of the Urach geothermal anomaly (Haenel 1982) and a proposed deep continental dnllhole (Alfred-Wegener-Stiftung 1985) seismic reflection and refraction surveys were carried out in Southwest Germany in 1978 and 1979 in the Urach area (Bartelsen et al. 1982; Gajewski & F'rodehl 1985; Walther et al. 1986) and in 1984 in the Black Forest and Hohenzollemgraben and adjacent areas (Fuchs et al. 1986; Gajewski et al. 1986; Gajewski & Prodehl 1986, Liischen et al. 1985; KTB Research Group Black Forest, this issue; Wenzel et al., this issue). This contribution will deal with the seismic-refraction survey of 1984 (Fig. 1). 2. The upper crust of the Black Forest The data, of which zyxwvu an example is shown in Fig. 2, will be discussed in some detail for the Black Forest line S, but the same basic features hold also for the other two lines U and Z (Fig. 1). The traveltime curves shown in the record sections (Fig. 2) are re-calculated from the corresponding velocity-depth cross section (Fig. 3a). The whole data set is represented and discussed in more detail by Gajewski & Prodehl(l986). In order to enable immediate comparison with the seismic-reflection data of KTB Research Group Black Forest (this issue), a simplified line drawing after Liischen et af. (1985) is shown in Fig. 3c onto which the main features of the seismic-refraction model (Fig. 3a) have been superimposed. The first-arrival phase a, refracted in the basement with a velocity of 5.9 km/s is followed by a reflection (phase a,) from the upper boundary of a low-velocity zone (dotted area in Fig. 3a and c). That zone is very accentuated under the northern and central Black Forest and is characterized by a velocity decrease from 6.2 to zyxw 5.4 km/s between 8 and 14 km depth. Toward the south, the velocity inversion gradually loses its intensity. Downloaded from https://academic.oup.com/gji/article-abstract/89/1/333/673316 by guest on 15 June 2020