HR: 1340h
AN: G53B-0885    [Abstracts]
TI: From Ground Deformation to Magmatic Source Processes, Why Simple Elastic Models are not Enough: Examples from Long Valley Caldera, California, USA
AU: * Newman, A V
EM: andrew.newman@eas.gatech.edu
AF: Georgia Institute of Technology, Earth and Atmospheric Sciences ES&T Room 2254, Atlanta, GA 30332 United States
AU: Dixon, T H
EM: tdixon@rsmas.miami.edu
AF: University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, 4600 Rickenbacker Causeway, Miami, FL 33149 United States
AU: Gourmelen, N
EM: ngourmelen@rsmas.miami.edu
AF: University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, 4600 Rickenbacker Causeway, Miami, FL 33149 United States
AB: The massively explosive eruptions that produce large silicic calderas such as Long Valley in California are among the most violent geological phenomena on Earth. With ever increasing populations and infrastructure being built near such volcanoes, the hazards posed by devastating caldera eruptions are ever increasing. After at least 100 years of calm, Long Valley caldera has, in the past 25 years, actively begun uplifting, generating tens of thousands recordable earthquakes and significantly altering it's geothermal system. Though comparisons with activity at other volcanoes suggest that an eruption is not imminent, our understanding of the physical processes underlying these volcanoes is incomplete, and the potential for future eruptions remains significant. Because of the recent activity, and abundant and diverse geodetic, seismic and geologic datasets available at Long Valley, the system remains a near-ideal study area to learn about the magmatic plumbing system before an eruption occurs. Unfortunately, geodetic modeling of volcanic activity generally averages data over long intervals and uses homogeneous Poisson solids to simplify fits to data. However, since well developed silicic systems generally have complex compositions, have a strong heat gradient near the source, and rapidly varying activity, these models can lead to inadequate results. Here, we use the available geodetic data (including EDM, GPS and InSAR) available from Long Valley's recent activity along with seismic (tomography and microearthquake locations) and geologic (caldera structure and strength) data to show how local rheology, including weakened and time-dependent viscoelastic crust, and volume significantly changes the estimates of pressure, shape and depth of the source of activity. These are important parameters for understanding the physical processes in a shallow magmatic system prior to eruption, and are necessary to better constrain in order to improve eruption forecasting and prediction.
UR: http://shadow.eas.gatech.edu/~anewman/meetings/AGU_F2005
DE: 7280 Volcano seismology (8419)
DE: 8419 Volcano monitoring (7280)
DE: 8428 Explosive volcanism
DE: 8440 Calderas
DE: 8485 Remote sensing of volcanoes
SC: Geodesy [G]
MN: Fall Meeting 2005