抄録
Deformation of thrust structure is generally reconstructed by using the geometrical balanced cross section method. Ramp angle, its length, volume of hangingwall displacement on the detachment and thickness of sediments deformed on the ramp control the analyzed fold structures. These geological elements are directly influenced by a state of subsurface stress and rock properties. However it is difficult to include the influence of rock properties in the section which is constructed in geometrical balancing.
In this paper, two geological sections in the Niigata basin are reconstructed by the Virtual Basement Displacement (VBD) method (Kodama et al., 1985), which simulates deformation and fracturing of the strata in a sedimentary basin. The distribution and magnitude of the strain concentration and fractures in these sections were analyzed quantitatively. The result of the simulation suggests that the strain is concentrated around volcanic bodies and reactivation of basement fractures in the well MITI Niigata-heiya section A-A', and some anticlinal anomalies had existed in deeper part of synclinal area in the section B-B' during the structural deformation history. The folds are formed with vertical displacement and the shortening volume of the folds seems to be less than the result of the balanced cross section of the geometrical method.
We can comprehend some tips, images and ways of thinking during the numerical analyses considering dynamic picture and kinematic picture. The understanding of rock properties and subsurface stress will lead us to effective exploration, especially to assess the thrust structures.
