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.

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In the previous paper, wave phenomena which are seen along the surface of a semiinfinite elastic solid subjected to an impulsive line force were studied, and many interesting results about the wave generation were obtained.
In the case of the line source, however, the peak of Rayleigh waves and the displacements at the origin become infinite, we cannot make any quantitative discussions about the wave form or particle orbit.
To remove these difficulties, we adopted here the force of some spacial width in place of the line source.
The noted results thus obtained are as follows;
1) For the normal (tangential) force of some width, we have no upward (backward) peak of Rayleigh wave up to some distance corresponding to the width. The upward (backward) peak of Rayleigh wave appears at some distance and grows up to decrease gradually.
On the other hand, the downward (forward) peak of Rayleigh wave is large at first and decreases gradually.
As time goes on, the amplitude of the upward (backward) peak becomes approximately equal to the downward (backward) peak.
2) For the normal force, particle orbit is anticlockwise at any point. While, for the tangential force, it is rather complex, and consists of two types of motion. At first, particle orbit is clockwise, but it becomes anticlockwise as soon as Rayleigh wave arrives.

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