Fig. 7

Diagram illustrating the two stress regimes in relation to the vertical stress (Sv). Stress magnitudes increase from left to right. For each region, the value of the intermediate principal stress (S2) relative to the maximum (S1) and to minimum principal stress (S3) is based on the computed Φ values. Sv is assumed to be equal for both regions. In the Helvetic domain Sv = S2 (strike-slip regime) while in the Penninic domain Sv = S1 (normal-faulting regime). The length of each horizontal bar is proportional to the differential stress needed to trigger an earthquake on an optimally oriented fault under the two stress regimes. It follows that both differential and absolute stresses are higher in the Helvetic than in the Penninic/Austroalpine domain