Kluftmessungen im Gelände und ihre Bedeutung für die Bestimmung des tektonischen Spannungsfeldes in der Schweiz

An intensive program of measurements of the orientation of joints in the field in Switzerland was undertaken in the Cantons of Graubünden, St. Gallen, Schwyz, Uri, Zürich, Zug, Aargau and Berne. For every «region», comprising 2–8 outcrops, the average orientation of the joint-parallelepiped was calculated by means of an electronic Computer based on a function-minimization program. If it is assumed that the steeply-dipping Joint surfaces have been produced by the present-day triaxial stress field according to the Mohr-Anderson theory of faulting, the orientation of the latter can be calculated. Thus, the net of present-day stress trajectories for Switzerland can be drawn. It turns out that the average orientation of the greatest compression in the region investigated is N 60^°W. This agrees well with in-situ stress determinations by Gysel in the Sonnenbergtunnel near Lucerne (N 76.5^°W) and by Greiner in southern Germany (N 28^°–50^°W). Converseiy, the hypothesis that most joints visible on fresh outcrops are due to the present-day tectonic Stresses and that the latter is homogeneous over extended areas, is thereby confirmed