HR: 08:15h
AN: V41B-02    [Abstracts]
TI: Characteristics of the Upward Flow of Magmatic Volatiles in the Volcano Conduit Prior to an Explosion Derived from the Broad-band Seismic Records
AU: * Zobin, V M
EM: vzobin@cgic.ucol.mx
AF: Observatorio Vulcanologico, Universidad de Colima, Av.Gonzalo Sandoval 444, Colima, Col 28045, Mexico
AU: Reyes, G A
EM: gard@cgic.ucol.mx
AF: Observatorio Vulcanologico, Universidad de Colima, Av.Gonzalo Sandoval 444, Colima, Col 28045, Mexico
AU: Guevara, E
EM: ego@cenapred.unam.mx
AF: CENAPRED, Av. Delfin Madrigal 665, Mexico, D.F 04360, Mexico
AB: A typical broad-band seismic record of Vulcanian explosion consists of two impulses, of low-frequency (LF) and high-frequency (HF) contents. We propose a conceptual model that considers the LF seismic signal as being generated by the vibration of the magma conduit during the upward flow of magmatic volatiles to the magma-free surface, while the HF seismic signal is generated by the explosion at the magma-free surface. We define the time D, representing the movement of magmatic volatiles, as the time from the beginning of LF impulse to the beginning of HF impulse and use the Fourier spectrum of the HF impulse to estimate the energy of explosion. Observations at two andesitic Mexican volcanoes: Volcan de Colima and Popocatepetl, indicated three depth levels for the beginning of the vertical movement of magmatic volatiles in the conduit at different stages of the eruption. The D values observed before significant Vulcanian explosions at both Mexican volcanoes are close, indicating similar depths of the beginning of vertical movement of magmatic volatiles. It is shown that there is a dependence of the energy of the explosions upon the duration of D.
DE: 7280 Volcano seismology (8419)
DE: 8428 Explosive volcanism
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly