Start |Author Index | View Uploaded Presentations | Meeting Information

Earth System Processes - Global Meeting (June 24-28, 2001)

Paper No. 0
Presentation Time: 4:30 PM-6:00 PM

PHYSICAL PROPERTIES AND MINERALOGY OF THE GRANITE FROM THE HIRABAYASHI HOLE (JAPAN)


SURMA, Fabrice1, GERAUD, Yves1, ZAMORA, Maria2, PEZARD, Phillipe A.3, BOULLIER, Anne-Marie4 and ITO, Hisao5, (1)Ecole et Observatoire des Sciences de la Terre (ULP Strasbourg), Centre de Géochime de la Surface, 1 rue Blessig, Strasbourg, 67084, France, (2)Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75252, France, (3)Laboratoire de Tectonophysique du CNRS, ISTEEM - Université de Montpellier 2, Place Eugene Bataillon - cc49, 34095 Montpellier, Cedex 5, France, (4)LGIT-IRIGM BP53 38041, Grenoble, Cedex 9, France, (5)Earthquake research Departement, Geol Survey of Japan, 1-1-3 Higashi, Tsukuba, Ibaraki, 305-8567, Japan, surma@illite.u-strasbg.fr

The 625m depth Nojima fault zone near is one of the major faults that implied the "Kobe" Earthquake (M=7.2) in 1995. In Japan, the GSJ Hirabayashi hole crosses this important zone and is studied to look at the relationships between deformation, alteration and physical properties of the granite. The host rock was highly fractured and altered and the lithology is primarily granodiorite. Physical properties were studied in the borehole by login and on cores recovered from the borehole (P and S wave velocities and attenuation, electrical properties, and some porosity measurements).

The aim of this study is to characterise the structure of the porous media from the cores, the evolution of porosity and the threshold repartition within the borehole. Tortuosity and morphology of void (surface properties) are observed by SEM. STEM observations and analysis on clays are performed on 30 samples coming from the GSJ borehole. Electrical, elastic and anelastic properties are compared to porosity, fracturing intensity and alteration.

The first results show a variation of porosity in a range of 0.2 to 4 %. The pore threshold and the void shape vary with alteration and fracturing intensity. As expected, porosity is inversely related to F (the formation factor) and also to tortuosity and altered matrix fraction. We see that anisotropy of P-wave velocities strongly increases with porosity. Secondary minerals occur within the matrix and along the fractures and cracks. Porosity modifications are induced by secondary mineral formation and by strain. These modifications have an influence on transfer properties and therefore on physical properties. Finally, there is a relationship between the porosity network and the type of strain.

Influence of matrix porosity during deformation has to be taken into account to understand the mechanism of deformation in the presence of fluid. The water rock interactions in the matrix volume and the presence of secondary minerals influence the deformation as well.

Session No. 12--Booth# 0

T10. Coupled Earth Processes: Deformation, Chemical Reaction, and Heat in Fault- and Fracture-Dominated Fluid Flow (Posters)
Monday, 25 June 2001: 4:30 PM-6:00 PM
© Copyright 2001 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.
Back to: T10. Coupled Earth Processes: Deformation, Chemical Reaction, and Heat in Fault- and Fracture-Dominated Fluid Flow (Posters)
<< Previous Abstract | Next Abstract >>