[Abstract]

We investigate the effect of movement of nearby fault caused by an intrusion of dyke on volcanic activity. We examine two factors as indicators of the effect of faulting. One is a change in stress concentration at the dyke tip and the other is a change in opening of dyke. In this study, a finite element method is applied under a two dimensional plane stress state to incorporate geometrical relationship between the dyke and the fault. Dyke and fault are modeled as an open crack with internal pressure and a shear crack with Coulomb friction, respectively. Geometrical parameters considered are an angle, a distance between the dyke and the fault, and the length of fault. One of the most important results is as follows; when a fault with high angle against the dyke strike extends beyond the dyke tip along the propagation direction, and when the fault with low angle extends to it, the dyke propagate and open more easily than the case without fault. We apply our result to recent volcanic activities in Japan associated with the dyke intrusion, the 1986 Izu-0shima and 1989 off Ito eruptions, and we suggest that changes in volcanic activities may have been attributed to the occurrence of moderate-sized earthquakes near the dyke tip.

e-mail:

hashimoto@rcep.dpri.kyoto-u.ac.jp