Fig. 5

Calculated stress drop as a function of hold time for regions dominated by quartz and clay minerals. In the calculation using experimentally determined healing rates equal to 0.014 for quartz and 0.001 for clay minerals, effective stress was assumed to be 100 MPa, and the stress accumulation yields 11.9 MPa for quartz and 0.8 MPa for clay minerals during an inter-seismic period of 10 years