Brittle Creep Damage as the Seismic Signature of Dyke Propagations within Basaltic Volcanoes
Résumé
Contemporary to nine dyke intrusions on Piton de la Fournaise, Etna, and Miyakejima volcanoes, we recover stationary seismicity rate and energy release over time, whether the dyke reaches the surface or not. This generic seismicity pattern for the dyke propagation of low viscosity magma argues for the fluid driven crack propagation to be a scale independent stationary process. This prevents any prediction of the time to eruption during the dyke propagation phase using seismicity rate alone. The seismic signature of the volcano deformation triggered by dyke injections corresponds to brittle creep damage in a strain driven setting. Whether mechanical properties of host rock structure or geometrical effects influence this generic stationary response is not resolved by the seismic data. Because a few, if any, aftershocks are resolved contemporary to dyke intrusion, the seismicity is purely driven by the dyke dynamics, that is, a proxy for the dyke volumetric growth.