Characteristics of crustal-stress distribution are necessary to study phenomena relating to tectonic activity. Analysis of the factors influencing this distribution has been rarely conducted. One of the reasons for this is in-situ stresses have not been adequately measured. Another reason is data measured in each site reflect the site's geological and tectonic conditions in a complex way. In-situ stress data which are regionally and vertically dense have been obtained in hard (granitic) rocks around the Kofu basin and near Mt. Tanzawa. This makes it possible for us to compare stress distributions between hard and soft rocks. Some of our sites located in hard rocks show a fluctuating stress distribution with depth. One other site shows that stress increases with depth monotonously as in soft rocks. Log data from each site suggest that this difference of stress distribution is under the influence of lithological heterogeneity. However, a linear relationship between shear stresses and effective normal stresses is obtained. The frictional coefficient changes in each site depending on each geological and tectonic setting. This suggests that the yielding caused by the frictional sliding of microfractures controls the stress distribution in hard rocks, as similarly observed in soft rocks.
