Correlation Between the Coulomb Stress and Occurrence of the Large Induced Seismicity at Basel, Switzerland in 2006

摘要

One of the critical problems in the development and operation of enhanced geothermal systems and hydrothermal reservoirs is the occurrence of felt earthquakes. Having previously shown that increases in pore pressure did not trigger the widely felt induced events observed at Basel, Switzerland, in 2006, we considered the possible triggering role of stress redistribution caused by preceding seismic events. We calculated static stress redistribution on the fault planes of the large events that were induced by preceding events, using the Coulomb 3 software package to model stress redistribution on a single fracture in a uniform crust. We found that average Coulomb stress decreased on many of the fault planes of the large events, bringing stability to the fractures. Although portions of the fault plane of the largest event showed positive changes in Coulomb stress, our modeling did not show a significant increase in Coulomb stress on this fault plane around the time of that event. We conclude that static stress redistribution did not trigger these large induced events. We also did not find any evidence that the magnitude of the events was correlated with static stress redistribution. Instead, stress redistribution in the fracture network, changes in the friction coefficient, or some undiscovered phenomenon may be the trigger mechanism.