Publikationsdatum:
1993-01-01
Beschreibung:
A slickenside was discovered from a boring core sample 1,880m deep in the Matsushiro earthquake swarm region in Nagano Prefecture, Japan. The slickenside has been considered to be created by earthquake faulting during the earthquake swarm period, because it accompanied fresh rock powder produced by earthquake faulting. The power spectral density of the topography of the slickenside was measured with a stylus profilometer over the wavelength range from 10-4 to 10-2m. Each profile of the surface has a “red noise” power spectrum over the wavelength range studied, with the power falling off on average between 2 and 3 orders of magnitude per decade decrease in wavelength. Meanwhile, the topography of the slickenside is found to show anisotropy in the spectral amplitude; the amplitude perpendicular to the slip direction is two to four times as large as that parallel to the slip direction. A generation mechanism for such topographic anisotropy is numerically modeled from a viewpoint of the fracture mechanics. It is supposed that the crack tip stress distribution in the plane parallel to the slip direction is represented by a model of a plane strain shear crack (Mode II crack) and that the stress distribution in the plane perpendicular to the slip direction is represented by an antiplane strain shear crack (Mode III crack). The stress field around the crack tip in the Mode III case shows a broader distribution with respect to the azimuth than that in the Mode II case. This difference of a stress field at the crack tip between the Mode II and the Mode III is a possible cause of the topographic anisotropy. © 1993, The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan. All rights reserved.
Print ISSN:
0022-3743
Digitale ISSN:
1884-2305
Thema:
Geologie und Paläontologie
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