抄録
A model called strength distribution model is proposed for elucidating the fracturing process of intact rock specimens under tri-axial loading of compression. This model provides a way to estimate the fracture stress from the relationship between crack density and applied stress for the specimens. Making use of the model, the fracture stress is estimated from the observed relationship in the range of applied stress from the onset of loading to the arbitrary upper bound. The estimated stress is found to be in agreement with the observed one with an error smaller than 1%, whenever the upper bound is taken to be more than 95% of the fracture stress. This model is also applied to the seismic activities prior to the 1989 Loma Prieta earthquake and to the 1996 Adak earthquake. The occurrence time and the magnitude respectively are estimated to be almost equal to the observed ones for both the earthquakes, Although more studies are needed to conclude, these results imply that earthquakes occur in principle following the same law as fracturing of intact rocks. The results of the fracture stress estimation for intact rocks may suggest that the long-term prediction of earthquakes is possible several years before the target earthquake with an error of about one year in the best case, provided that the recurrence time of the earthquake is about a hundred years.
