HR: 0800h
AN: V11B-1435    [Abstracts]
TI: The effects of heat flow on low-frequency events
AU: Sturton, S
EM: sturton@min.uni-muenchen.de
AF: Department fuer Geo und Umweltwissenschaften, Theresienstrasse 41/111, Muenchen, 80333 Germany
AU: * Dingwell, D
EM: Dingwell@lmu.de
AF: Department fuer Geo und Umweltwissenschaften, Theresienstrasse 41/111, Muenchen, 80333 Germany
AB: At many volcanoes the frequency content and waveforms of low-frequency seismicity is observed to vary over different timescales. At Soufriere Hills Volcano, Montserrat, single hybrid events merge into tremor and occasionally gliding lines are observed in the spectra indicating changes in the seismic parameters with time or varying triggering rates of single events. At Redoubt Volcano, Alaska more gradual variations are seen over longer timescales when the waveforms of a swarm of long-period events evolved gradually during a 23$\,\rm$hr time period. We consider the influence of heatflow on the seismic signal. Simple analytical solutions for heat flow are used to estimate the temperature gradient between the magma and country rock at increasing time intervals after the initial emplacement of magma. The seismic parameters and density are modelled by applying a tapering function of a similar shape to the numerical solutions between the seismic properties in the rock and those in the magma. The seismic wavefield for the conduit is modelled using a finite difference code. The effects of the taper on the seismic signal are considered for a range of acoustic parameters and timescales. The results show the long term variations that could be caused by heat flow and therefore facilitate the interpretation of variations in of the waveforms of low-frequency events.
DE: 8400 VOLCANOLOGY
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting