Modelling of processes in earth realistic heteorogenic crust

Geological and geophysical techniques aim to reveal crustal processes by observing various derived changes. This would be relatively simple if the earth could be assumed to be rheologically homogeneous in all cases. However, simplifying such conditions may be very misleading. Within the PRENLAB projects there has been significant success in applying analytic crack theory to explain the response to applied stresses in proximity of rheological discontinuities. Models which have been developed help to interprete induced seismicity in rift zones in response to stress changes. Other models help to interprete faulting and deformation at depth based on surface observations. Such results are described in Subproject 7, Subpart 7A.

A model was created of the space-time development of stress field in the SISZ on basis of historical earthquakes and expected tectonic loading. Modelling of stress field due to plate motion and the sequence of strong earthquakes since 1706 showed that the events released stress in the whole volume of the E-W trending SISZ despite that they take place on N-S faults. The earthquakes in most cases occurred in areas where the model shows relatively high stress at the time of the events. This was also partly true for the two large earthquakes of June 2000 as described under Subproject 7, Subpart 7B.