Thermally induced stresses beneath the Vrancea area, Integrated research on the intermediate depth earthquake genesis within Vrancea zone

The Vrancea seismic area, in Romania, is a place where intermediate-depth earthquakes occur as a result to stress generation in a cold descending lithosphere, as recently revealed by inversion of P-wave seismic velocity anomalies into temperature. A numerical calculation of the stresses associated with the negative temperature contrast beneath Vrancea results in a high concentration of thermally induced stresses. A predicted stress pattern consisting of horizontal compression and vertical extension agrees with observation of stress at depths of 70-200 km. High shear stress is also consistent with the location of seismogenic volume, and the predicted stress magnitude in this region is >200 MPa (in good agreement with the unusual stress drop at the source). Our model shows that thermally induced stresses beneath Vrancea could play a significant role in the generation of intermediate-depth earthquakes.