Stress orientations found in north-east Germany differ from the West European trend

Knowledge about the acting stresses is of crucial importance for understanding the tectonics of a region. Data about the stress field in north-eastern Germany used to be very rare. In general, it was assumed that the orientation of the larger horizontal principal stress (S_H) is similar to that found for western Germany and central West-Europe, i.e. NW–SE. To check this, several borehole logs of the late 1980s were analysed for information on the principal horizontal stress orientations: they include Four-Arm-Dipmeter and borehole televiewer data from 15 boreholes. The depth range of our stress results reaches from 1500 to 6700 m. They were compared to a few other data, especially from hydraulic fracturing, and to recent findings on the stresses in the Northwest German basin. In contrast to expectation, S_H derived from breakout orientations below the salt layers displayed N to NE orientation. The latter was found at 10 locations spread over the NE-German basin from Berlin to the Baltic sea, from the Polish border to the former border between East and West Germany. Moreover, this stress rotation in the subsaline formations seems to be the continuation of a trend found in the NW German basin.