THE SEISMIC SIGNATURES OF THE VOLCANIC CRISES: A REVIEW

Volcano seismology is considered a good proxy of the internal conditions of the volcanic systems. In particular, the volcanic crises are anticipated by a loading process triggered by an overall upward magma migration inducing gas exsolution and stress build up within the feeding system and the hosting rocks. This process activates brittle failures within the volcanic edifice and pressurized magmatic fluids flowing through magma-filled cavities, generating the two end-members of the volcano seismicity: Volcano-Tectonic and Long-Period events, respectively. Volcano seismicity follows the disequilibrium conditions within the plumbing system preceding and accompanying the volcanic crises, exhibiting modifications of the source process in respect to the inter-eruptive phase in terms of wavefield properties and statistics of the earthquake occurrence. Although some common correlations between seismic activity and magma dynamics during the eruptive crises have been identified, a wide variability of behaviors appears as well, with a sharp dependence on the volcano and on the eruptive episode. Here I critically review the characteristics of the volcano seismicity before and during the volcanic crises, describing the source process of the volcanic earthquakes in terms of both the seismologic parameters and the statistical properties of the point process ruling their occurrence times and magnitude.