Crustal Stresses Inferred from Fault-Plane Solutions of Earthquakes and Neotectonic Deformation in Switzerland

Abstract

P-axes inferred from fault-plane solutions of 23 recent earthquakes in Switzerland and adjacent areas reveal a NNW — SSE (E Switzerland) to NW — SE and WNW — ESE (W Switzerland) orientation of maximum horizontal compressive stress in the upper crust. Nearly the same orientation of maximum compression is indicated by in situ stress measurements. The orientation of maximum horizontal compressive stress corresponds well with the orientation of maximum horizontal crustal shortening as derived from a kinematic analysis of Neogene and Quaternary structural features. Evidently the stress field which causes the present seismicity is very similar in its orientation to the stress field of the last 5 to 10 million years which produced the neotectonic deformation. In several cases of earthquakes in the Helvetic Alps, the Lake of Constance area and in the Jura Mountains a distinct relation between the parameters of the fault-plane solution and neotectonic deformation is shown up.