SEMINAR: GEOTOPICS Presrnts: Volcanic Conduit Dynamics: A Multidisciplinary Approach to Modeling Low-Frequency Volcanic Seismicity

[orash sharifi <osharifi@rsmas.miami.edu>]

Monday, April 9, 2012
3:15, SLAB Seminar Room, S/A 103
Refreshments at 3:00 PM

Our upcoming speaker is Dr. Gregory Waite , visitor scientist from Michigan Technological University

The title of his talk is "Volcanic Conduit Dynamics: A Multidisciplinary Approach to Modeling Low-Frequency Volcanic Seismicity"

Abstract
The interaction of multiphase fluids with the volcanic conduit produces a variety of measurable low-frequency seismic signals. Tremor and long-period earthquakes (0.5-5 Hz
frequency) result from fluid migration and/or convection, and resonance in fluid-filled conduits. Modeling of so-called, very-long-period earthquakes (60-10 s period) suggests they result from conduit deformation associated with mass advection or large pressure changes. Both LP and VLP earthquakes are commonly repetitive so a complete description of their source processes may explain fundamental characteristics of magmatic fluid transport. However, source models derived from waveform inversion typically leave abundant room for speculation about the role of volatiles. In order to better constrain the models, we are collecting infrasound and ~1 Hz SO2- emission data together with broadband (60 s - 50 Hz) seismic data at several active volcanoes. The additional data streams provide important constraints on the mechanisms responsible for low-frequency seismicity. As an example, the plot shows the correlation between the occurrence of very-long-period earthquakes (7 spikes in the blue filtered vertical channel seismogram) and variations in SO2 emission (red dots) during gas puffing at Fuego Volcano Guatemala. Each dataset offers a quantitative estimate of the amount of gas responsible and the timing is used to constrain details about the path the gas took through the top of the conduit. In this case, we attribute the VLP events to gas accumulation on a time scale of 5 minutes and release through a system of cracks on a time scale of less than a minute. In other cases, infrasound data have helped to constrain the mechanism of long-period events and tremor. I will discuss our seismic modeling and interpretation using multiple data streams and the implications for eruptive styles at Fuego Volcano and others.

We hope to see you all there!

Your GEOTOPICS Coordinators,

Keri Vinas and Arash Sharifi