A study of anisotropic granodiorite from the 1982 Miramichi earthquake epicentre

Abstract

Granodiorite samples taken from the epicentre of the 1982 Miramichi earthquake sequence reveal a parallel network of Mode I (tensile) fractures. These fractures have a marked effect on the mechanical properties of the material as determined by laboratory testing. The action of stress cycling produces a pronounced decrease in strength of the material as permanent strain is accumulated by dilatant behavior. The micro-fractures are believed to have formed in response to a stress regime whose maximum principal stress orientation is approximately horizontal, east-west trending and whose minimum principal stress is vertical.