HR: 1340h
AN: G43B-1193    [Abstracts]
TI: Geodetic and Modeling Constraints From Ongoing Uplift at Long Valley Caldera: Continued Episodic Dome Growth Observed in 2002-2003
AU: * Feng, L
EM: lfeng@gatech.edu
AF: Georgia Institute of Technology, School of Earth and Atmospheric Sciences, 311 Ferst Drive, Atlanta, GA 30332, United States
AU: Newman, A V
EM: anewman@gatech.edu
AF: Georgia Institute of Technology, School of Earth and Atmospheric Sciences, 311 Ferst Drive, Atlanta, GA 30332, United States
AB: Long Valley Caldera (LVC), a 17×32 km² collapse crater in eastern California, sits on the eastern edge of the Sierra Nevada Mountains. Beginning around 1978, scientists observed signs of renewed unrest and developed a monitoring network including continuous seismic and geodetic observations. From that point, overall uplift of the central resurgent dome is estimated to be nearly 80 cm, from episodic events beginning around 1979(?), 1989, 1997 and 2002, along with interim periods of long-term uplift, inactivity, or slow deflation. While an understanding of the dynamics of this complicated time-history remains elusive, we focus here on the previously undescribed episode which occurred between 2002 and 2003. We use the continuous regionally filtered 3- component GPS data processed by the USGS, from which we remove the motion of the Sierra Nevada Block relative to North American plate (defined by Dixon et al., [2000]). Like deformation from the previous episodic uplift and interim periods, uplift is mostly radial, and can mostly be explained by a single source located just west of the central resurgent dome. The maximum uplift during the 2002-2003 episode is ~35 mm, about 1/3 the size but with a similar exponential shapes as the 1997-1998 episode.
To better understand the dynamics of the system, we develop numerical finite-element models (FEM) to study the 2002-2003 inflation episode and determine the sensitivity of topography, layered rheology, and the presence of ring fractures on deformation. We find that while topographic effects are minimal, the choice of values for layered rheology and the existence of the south moat can contribute significantly to variations in observed deformation, and obscure the source location, particularly depth.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1211 Non-tectonic deformation
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 8419 Volcano monitoring (7280)
DE: 8440 Calderas
SC: Geodesy [G]
MN: 2007 Fall Meeting