Micromechanics in frictional dynamics of faults

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This project has been carried out to investigate the contact mechanics between two rough surfaces.First of all,measurement method of surface topography was examined by use of a three dimensional surface profilometer. A new data acquisition method was proposed. Paper 1( see below ) has been submitted in which the results are included. We also performed a computer simulation using the three dimensional surface data acquired by the method mentioned above. We found that plastic behavior of contacting asperities plays an important role and hysteresis in loading and unloading processes can be explained by the plastic behavior. The results were reported in Paper 1.A series of experiments have been conducted to investigate wave transmission across a contacting surface. Comparing the experimental results with the theory of wave transmission, we found that a joint behaves visco-elastically to high frequency transmission P- and S-waves. The results have been presented in the Paper 2( see below ).As to the initiation of slip, two papers have been published which are shown on the other side of this report. The mechanics of initiation of slip were precisely studied and the experimental results were compared with a contact theory. The theory successfully explains the experimental results. Thus we can understand the mechanics of initiation of slip more precisely than previously done.All the results obtained in this project were reported in a separate volume.Paper 1 N.Yoshioka, Elastic and plastic behavior of contacting surfaces under normal load: A computer simulation using three dimensional surface topographies, submitted to J. Geophys. Res.Paper 2 N.Yoshioka and M.Kikuchi, Visco-elastic response of joints to transmission waves, submitted to Geophys. Res. Lett.