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

This paper studies the effects of strain sources at depth, simulating volca nic source activation, on the changes of Coulomb failure stress in the surr ounding volume. Such simulations are aimed at clarifying the relationship b etween volcano dynamics and seismicity generated by stress changes. The eff ect of isotropic overpressure or dike opening on the Coulomb stress pattern s is shown here, in presence of a background tectonic stress. Seismicity pa tterns 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 pe rformed, showing that seismicity at this area is well explained by stress c hanges produced by rift opening (i.e. without any contribution out of local sources), both in terms of location patterns and focal mechanisms. In part icular, the widely observed focusing of seismicity in the southern flank ca n 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 s eaward sliding of the Southern flank, on the low-angle reverse faults hypot hesized at the base of the rift zone. (C) 2001 Elsevier Science B.V. All ri ghts reserved.