The seismicity in the region north-west of the Alps is moderate but significant earthquakes can occur (1356 A.D. Basel earthquake, 6
Few deep stress measurements exist so I study focal mechanism inversions methods. They have the advantage to provide stress orientations at seismogenic depths. Several methods of focal mechanism inversion have been developed over the years to determine the principal stress orientations. I compare three of the most common ones to determine the method better adapted to my problem. Moreover before applying these methods, the dataset must be checked to see wether it verifies the physical assumptions made by each method.
from Maury et al., 2012
Principal stress directions determined with the three methods using a dataset composed of independent events. The solution in blue is determined with Angelier's method. The solution in red is determined with Michael's method. The solutions in shades of grey are determined with Gephart and Forsyth's method. Two minimas are found. The minimum principal stress direction calculated in Basel borehole is shown in reen hatches.
Finally I have to take into account the Moho which is a major density contrast and the lithosphere-asthenosphere boundary (LAB) which is the base of my model.
The main features of my model. The bigger slope is due to the dipping of the LAB under the Alps. The other important structure is the cenozoic rift system.
The variations of the geometry of the Moho are negligible before the variations of the LAB.
Taking into account these geometries and using an elasto-plastic rheology for the lithospher the principal stress directions can be reproduced.
Moreover the plastic zone identified with this model roughly correspond to the area of the most seismically active domain.