To consider the occurrene of earthquake, it is neccesary to know the mechanism of deformation and fracture of silicate rocks. Uuder the experiments of the short-time simple compression test, granites have the property represented by the Maxwell-Kelvin complex. Retardation time of the Kelvin body is about 7-9 seconds, independent of stress and rock classification. Fluidity of the maxwell body increases rapidly near the rupture, and the elastic after effect is increasing with stress multification.
The strain ratio of longitudinal to lateral direction is largely above the value of 0.5 for granites near the rupture, that is, there is volume expantion in this region. However, this effect does not arise instantaneously with loading, but depends on the plastic flow after stress added; and the longer the duration, the larger becomes the volume inflation. We suppose, it is because of cavity augmentation inner the specimen on the occasion of fracture.
