Abstract
Here we present new geophysical, geochemical, and mineralogical data from the high quality core samples recovered by air bubble boring at central Shikoku area, that belongs to the Sanbagawa Metamorphic Belt. The roundness of sand grains and quartz content become high value around the slip surface, which indicates that the fine graining of the matrix has been induced by fragmentation and/or weathering at the shear zones. In the Okishimo section, which consists mainly of the pelitic schist, the full width half maximum (FWHM) of the prominent basal reflections of clay minerals (chlorite and illite) show broadly peak around the slip surface. In the Kashio section with the lithologic boundary at the slip surface between pelitic and basic schist, the fine-grained matters and the values of magnetic susceptibility increase around the slip surface and the composite planar fabric characterized by brittle shear zone of the fault rock is recognized at thin section of the lithologic boundary. We also deduce that measurements of the clast capacity ratio and the equotip hardness test are useful for the understanding of the features of the slip surface and/or the state of fragmentation caused by landslides, and hope to apply these observations to the practical investigations for landslides.
