Abstract
For a vast dimension as that of the actual earth's crust, the effect of the gravity is very great as compared with the effect of strength of the material. Hence, the earth's crust may be represented by powder mass as a model in laboratory. In the present paper, the cohesion of powder mass was measured and it was found that they are about 0.4-0.02gr./cm2. Next the following similitude law of cracks was deduced where λ is the linear dimension of the fractured pieces, d the thickness of powder layer, ρ the apparent density of powder, g the acceleration due to gravity, Fs the cohesion of powder. This law was applied for geophysical problem, and it was concluded that the earth's crust has block structure. and its linear dimension was calculated as about 13km which is in good accordance with the observed value 10km.
