Hydraulic rock stress measurements in the Bjorko meteoritic impact structure, lake Malaren, Sweden

摘要

We have conducted a stress measurement campaign and analysis of in situ hydraulic rock stress measurements in the Bjorko impact structure, island of Bjorko in Lake Malaren, West of Stockholm, Sweden. An inversion method developed by Cornet (1993), based on the least squares criterion, was used to determine the horizontal stresses versus depth. The inversion results indicate that the horizontal stress magnitudes are slightly lower than the normal trend in Fennoscandia (Amadei & Stephansson, 1997). The orientation of maximum horizontal stress is NW-SE, from ～300 m and downwards.