Multi-Crack Characterization

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Results obtained during the research term (1993-1995) are summarized for each researcher in the following :(1) We investigated universal properties of fracture by numerical simulations. It was proven that strong macroscopic universality holds both in the cases of crack propagation model on a plane and of 3-dimensional impact fracture (Takayasu).(2) Asynthetic modelling of geothermal structure was developed which accounts for the heat discharge at the surface, the subsurface temperature, the electric resistivity structure, the Curie point depth and the inert gas composition of fumarolic gas (Yusa).(3) The multiple cracking behavior in rock was examined based on the fractal nature of acoustic emission (AE). It is demonstrated that the multiple cracking behavior in rock could be analyzed using a numerical model in conjunction with the AE results (Hashida).(4) The conditions for propagation and unstable oscillation of cracks were characterized by nondimentional fracture parameters for both … More single crack and multiple cracks (Sano).(5) A new method of detecting and monitoring fractures by use of seismic waves was proposed. The effect of injecting air into fracture was nvestigated by using both model experiments and numerical simulations. An AVO inversion method and a depth transform technique of seismic reflection data were developed. A current-convergent resistivity log by adding auxiliary sources was investigated (Sasa).(6) A fractal model to quantify the crack distribution in rock masses and a method to evaluate model input parameters by a lineament analysis of earth satellite image have been proposed. By applying the proposed method to a granite field, the crack distribution and the connectivity of cracks have been estimated (kaneko).(7) Analytical data of aero-photo and satellite images were compared with geologically identified natural fracture systems. Geologically undefined lineaments were traced by gamma ray survey. A new analytical method for satellite image was introduced (Takashima).(8) The fractal analysis on the 1500 faults of 6 groups suggests that the relationship between the width of shear zone and fault displacement, size (displacement) distribution, and the spatial distributions of faults and fault displacements show the fractal distributions whose fractal dimensions change depending on the ductility of rocks and the total energy density injected (Ohtsuki).(9) The structure of elastic wave velocity and density of the crust is known to be heterogeneous. Analyzing the well-log data obtained at 5 wells in Kyushu and Kanto, Japan, we found that their power spectra obey a power law for a wide range in wavelength from a few tens of centimeters to a few hundred meters (Sato).(10) Fractal dimensions of splitting fracture surface of welded tuff specimens using by divider method are nearly in inverse proportion to the strength. On the other hand, the coefficient of variation of dimensions near the pre-crack in CT specimens are nealry in proportion to the fracture toughness (Tano). Less