Advanced Spatial Modeling on Distribution and Physical Property of Faults for Predicting Hydraulic Phenomena over Ultra-long Term

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This study has characterized the fault functions for fluid paths and crustal movements from the following four points of data analyses, sample measurements, and field surveys. The fracture data obtained by rock surface surveys and deep drillings at the Kikuma and Toki granite areas in west Japan were used for the analyses.1. Two 3D spatial modeling methods, OPTSIM for discontinuous geologic layers and physical properties and GEOFRAC for fractures including joints and faults, were developed. A mechanical minimization criterion and a stochastic simulation were combined for OPTSIM. GEOFRAC incorporates the directions(strikes and dips)of the fracture data into the simulation. At first, fracture locations are generated randomly following fracture densities. Fracture directions are transformed into an indicator set consisting of seven binary variables and the variables are compressed using the principal component analysis. Kriging is then employed to estimate the distributions of these princ … More ipal values. Finally, element fractures are determined from the simulated locations and directions, and the fractures within the angle and distance tolerances are connected to form a fracture plane. GEOFRAC was shown to be able to depict a plausible fault system because the simulated directions corresponded well to those measured. In addition, regional hydraulic conductivities of fault zone were calculated by an inversion analysis of the subsurface temperature distribution.2. Spatial distributions of filling minerals of fractures were modeled, which contributed to specify the fluid paths through continuous fractures and faults.3. Lineaments detected from multi-shaded Digital Elevation Model were used as large-scale fracture elements. Using the simulated continuous fractures and lineaments, similarity on the dominant directions and the histogram shapes of length distributions were identified.4. A part of heterogeneity in fault dynamics and hydraulic property were clarified through measuring and analyzing the radioactive nuclides in the top soils on fault zones. Less