ABSTRACT
In order to survey rock stress states in the Japanese Islands, we added new measurement data to published data and arranged them about depth distribution and plane distribution. Collected data were measured at 122 points from 1971 to 2001 by stress relief method, hydraulic fracturing method and AE-DRA method. Each measurement is carried out in depths of less than 1600 m. The vertical and horizontal stresses are given as a function of depth below surface, especially vertical stress almost coincides with overburden pressure. Most of the ratio between horizontal maximum stress and vertical stress are observed in the range of 1 to 2. More than half of horizontal maximum stress directions are reconciled with crustal strain directions estimated from triangulation survey data.
