11. COMPUTED TOMOGRAPHY SCAN IMAGE ANALYSIS OF SEDIMENTS ¹

Juichiro Ashi ²

ABSTRACT

Three-dimensional high-resolution images of density distributions were obtained on unsplit cores using a medical X-ray computed tomography (CT) scanner. The resolution of CT scanning is about 0.6 mm² and allows a 5-mm depth for beam width. Electrical resistivity measurements were also conducted to know porosity at high depth resolution after core splitting. Whole-round core samples for this study were collected from Sites 948 and 949 in the northern Barbados ridge accretionary prism during Ocean Drilling Program Leg 156. On the basis of the relationship between densities and linear attenuation coefficients of standard samples, densities derived from CT scans are consistent with densities by the mass/volume method of all the samples irrespective of their compositions. Sample disturbance is easily detected in CT-scan images by convolutional texture in CT images perpendicular to core axes. This nondestructive technique provides reliable densities at high depth resolutions for evaluating disturbances by drilling or core splitting.

¹ Shipley, T.H., Ogawa, Y., Blum, P., and Bahr, J.M. (Eds.), 1997. Proc. ODP, Sci. Results, Vol. 156: College Station, TX (Ocean Drilling Program).
² Geological Institute, University of Tokyo, 7-3-1 Bunkyo Hongo, Tokyo, 113 Japan. ashi@geol.s.u-tokyo.ac.jp