CRUSTAL STRAIN IN SWITZERLAND 1870-1970

The rate of horizontal crustal deformation in western Switzerland has been determined from a comparison of two triangulation surveys, centred approximately on the epochs of 1872 and 1912, and a trilateration survey made around 1970. A heterogeneous strain model was needed to fit these data, and yielded a rate of (tensor) shear strain of about 0.10 ± 0.02 μrad yr‐1 in central Switzerland, with the axis of maximum relative shortening (compression) aligned approximately NW–SE, and the magnitude of the shear‐strain rate increasing to the SE. Along the chain of the Jura, the shear‐strain rate is about 0.05 ± 0.02 μrad yr‐1, with the axis of maximum relative shortening aligned NE–SW, parallel to the chain itself. This distribution of shear‐strain rate is consistent with a complex bending in the horizontal plane, in which the (concave) normals to the axes of maximum bending rate lie in the NW quadrant (i.e. in the opposite sense to the present curvature of the Jura). Copyright © 1990, Wiley Blackwell. All rights reserved