Magnetic Anisotropy of Andesites in a Fault Zone

Abstract

The saturation magnetic anisotropy of andesite in a fault zone is measured. It is found that anisotropy is more remarkable for samples closer to a fault and the origin of the anisotropy is essentially due to the shape alignment of magnetic grains in rocks. On the basis of these experimental results it is suggested that the fault movement is responsible for the observed shape alignment of grains in the rocks. Finally, from the measurement of the magnetic anisotropy in three mutually perpendicular disks cut from the rock samples, the direction of the fault movement is estimated.