HR: 16:45h
AN: V54B-04    [Abstracts]
TI: A Fracture-Mechanical Model of Crack Growth and Interaction: Application to Pre-eruptive Seismicity
AU: * Matthews, C
EM: c.matthews@ucl.ac.uk
AF: Benfield UCL Hazard Research Centre, Department of Earth Sciences, University College London, London, WC1E 6BT, United Kingdom
AU: Sammonds, P
EM: p.sammonds@ucl.ac.uk
AF: Benfield UCL Hazard Research Centre, Department of Earth Sciences, University College London, London, WC1E 6BT, United Kingdom
AU: Sammonds, P
EM: p.sammonds@ucl.ac.uk
AF: Mineral, Ice & Rock Physics Laboratory, Department of Earth Sciences, University College London, London, WC1E 6BT, United Kingdom
AU: Kilburn, C
EM: c.kilburn@ucl.ac.uk
AF: Benfield UCL Hazard Research Centre, Department of Earth Sciences, University College London, London, WC1E 6BT, United Kingdom
AB: A greater understanding of the physical processes occurring within a volcano is a key aspect in the success of eruption forecasting. By considering the role of fracture growth, interaction and coalescence in the formation of dykes and conduits as well as the source mechanism for observed seismicity we can create a more general, more applicable model for precursory seismicity. The frequency of volcano-tectonic earthquakes, created by fracturing of volcanic rock, often shows a short-term increase prior to eruption. Using fracture mechanics, the model presented here aims to determine the conditions necessary for the acceleration in fracture events which produces the observed pre-eruptive seismicity. By focusing on the cause of seismic events rather than simply the acceleration patterns observed, the model also highlights the distinction between an accelerating seismic sequence ending with an eruption and a short-term increase which returns to background levels with no activity occurring, an event also observed in the field and an important capability if false alarms are to be avoided. This 1-D model explores the effects of a surrounding stress field and the distribution of multi-scale cracks on the interaction and coalescence of these cracks to form an open pathway for magma ascent. Similarly to seismic observations in the field, and acoustic emissions data from the laboratory, exponential and hyperbolic accelerations in fracturing events are recorded. Crack distribution and inter-crack distance appears to be a significant controlling factor on the evolution of the fracture network, dominating over the effects of a remote stress field. The generality of the model and its basis on fundamental fracture mechanics results makes it applicable to studies of fracture networks in numerous situations. For example looking at the differences between high temperature fracture processes and purely brittle failure the model can be similarly applied to fracture dynamics in the edifice of a long repose volcano and a lava dome.
DE: 3235 Persistence, memory, correlations, clustering (3265, 7857)
DE: 4475 Scaling: spatial and temporal (1872, 3270, 4277)
DE: 5104 Fracture and flow
DE: 7280 Volcano seismology (8419)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting