2002 Volume 54 Issue 4 Pages 547-556
Associated with the western Tottori earthquake of October 6, 2000 (MJMA 7.3), the concrete lining of a headrace tunnel 200m below the surface in the epicentral area was faulted at two locations. In the eastern fracture zone, a NW-trending fault offsets the concrete lining 2cm left-laterally. Detailed total station mapping across the approximately 7-m-wide fracture zone reveals 10 to 20cm of left-lateral warping of the side walls of the tunnel. At the other location about 365m to the west, warping of the tunnel's side walls reveals left-lateral offset of approximately 2cm across the 4-m-wide fracture zone. It may be inferred that strands of the major faults associated with the 2000 western Tottori earthquake ruptured the tunnel 10 to 20cm left-laterally. Hence it appears that the total slip on the fault planes reduced from 1-2m at depth to 10-20cm near the ground surface.
