Poroelastic Response Resulting from Magma Intrusion

Abstract

The pore pressures that develop around magmatic intrusions in saturated porous media are of interest in both defining the characteristics of the intrusive process and evaluating the potential for destabilization of volcano flanks. Magmatic dike emplacement may be represented as an analog to a moving dislocation in a poroelastic medium, enabling parameters such as intrusion rate, volume, intrusion morphology and location to be determined from the form of the pressure history response. Solutions for moving point and line dislocations within infinite and semi-infinite media are reported as analogs to pencil and sheet dike forms, respectively. Where the mechanical and flow parameters of the system are defined, a priori, type curve matching of responses may be used to evaluate both emplacement location and intrusion volume, uniquely. For slow emplacement, the intrusion rate may also be determined. Poroelastic pressures developed around dike intrusions are substantial and may contribute to the triggering of deep seated earthquakes and the development of large-scale instability of volcano flanks. Recognition of the role of emplacement generated pore fluid pressures in the triggering of flank failure addresses the enigma in the failure of shallow inclination flanks of oceanic shield type volcanoes, in the absence of obvious sufficient destabilizing forces.