Stress changes associated with volcanic sources: constraints on Kilauea rift dynamics

This paper studies the effects of strain sources at depth, simulating volcanic source activation, on the changes of Coulomb failure stress in the surrounding volume. Such simulations are aimed at clarifying the relationship between volcano dynamics and seismicity generated by stress changes. The effect of isotropic overpressure or dike opening on the Coulomb stress patterns is shown here, in presence of a background tectonic stress. Seismicity patterns resulting from such stress changes can thus be used to shed light on the sources involved. Simulations of Coulomb stress changes associated to the opening of the Northeast rifts at Kilauea volcano (Hawaii) have been performed, showing that seismicity at this area is well explained by stress changes produced by rift opening (i.e. without any contribution out of local sources), both in terms of location patterns and focal mechanisms. In particular, the widely observed focusing of seismicity in the southern flank can be explained in terms of Coulomb stress changes generated by rift opening, once the different opposing masses in the northern and southern flank is taken into account. In addition, Coulomb stress changes due to rift opening are shown to explain both the occurrence of large earthquakes and of the seaward sliding of the Southern flank, on the low-angle reverse faults hypothesized at the base of the rift zone.