HR: 11:05h
AN: V52B-04    [Abstracts]
TI: Factors Determining the Propagation and Arrest of Magmatic Fissures
AU: * Taisne, B
EM: taisne@ipgp.jussieu.fr
AF: Laboratoire de Dynamique des Fluides Geologiques, Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75252, France
AU: Tait, S
EM: tait@ipgp.jussieu.fr
AF: Laboratoire de Dynamique des Fluides Geologiques, Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75252, France
AB: Volcanic eruptions are typically preceded by seismic swarms and ground deformations that result from the propagation of magma-filled fractures from a shallow reservoir or deeper source to the surface. However these sequences sometimes abort in the sense that a seismic crisis stops without an eruption taking place. The long term evolution of volcanic edifices is partly conditioned by whether magma erupts at the surface or stops as intrusions in the subsurface. The interpretation of these observations in terms of physical processes is an important and challenging scientific problem as well as one of potentially considerable operational value for observatories on active volcanoes. Analysis of several recent seismic crises at Piton de la Fournaise volcano using continuously recordings show that different patterns of seismic energy release can be recognised. We propose possible interpretations of these data based on the results of laboratory experiments in which constant volumes or fluxes of liquid are injected into elastic, brittle host material made with gelatin. Experimental conditions are either isothermal, or with a gelatin host temperature below the solidus of the hot liquid in the fracture: the latter causes solidification. Fracture propagation is driven by liquid buoyancy and/or elastic over- pressure, and resisted by fracture toughness, viscous stresses and or freezing. Constant volumes of liquid propagating due to buoyancy can stop even under isothermal conditions due to an effective fracture toughness of the host medium appropriate for the three-dimensional evolution of the fracture. Solidification in an advancing fracture enhances the effective toughness in the tip region and can lead to intermittent propagation in the case of constant flux and arrest of fractures in the case of decreasing flux.
DE: 5104 Fracture and flow
DE: 7280 Volcano seismology (8419)
DE: 8419 Volcano monitoring (7280)
DE: 8434 Magma migration and fragmentation
DE: 8445 Experimental volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting