HR: 16:00h
AN: V14B-01    [Abstracts]
TI: Imaging Dike Intrusion by Joint Inversion of Deformation and Seismicity
AU: * Segall, P
EM: segall@stanford.edu
AF: Geophysics, Stanford University, Stanford, CA 94305 United States
AU: Yun, S
EM: shyun@pangea.Stanford.EDU
AF: Geophysics, Stanford University, Stanford, CA 94305 United States
AB: Geodetic measurements of ground deformation, such as GPS and InSAR, allow researchers to infer the depth, geometry, and volume change (or pressure) of different volcanic sources. However, the resolving power of the deformation data is limited and decreases with increasing depth. Improved data distribution and signal to noise ratio increase resolution but there are fundamental limitations that will not be exceeded. One strategy for improving out ability to image processes at depth is to combine multiple data sets. Volcanically induced seismicity is stress dependent and therefore sensitive to details of the magma source shapes, specifically the gradient of the chamber wall displacement. Here we explore the possibility of joint inversion of seismicity and deformation data to improve resolution at depth. Magma intrusion causes stress changes, which alter the rate of earthquake production. DieterichA›ƒ,ªƒ,›s (1994, J.G.R.) seismicity rate theory, which is based on rate and state friction, allows one to map the stress change to the number of earthquakes in a given time interval after the stress change is applied. The forward function, along with geodetic GreenA›ƒ,ªƒ,›s functions, is called in a nonlinear inversion routine that solves for the geometry of a planar deformation source subject to a uniform pressure boundary condition (Yun et al., J.V.G.R., 2005). Model parameters aσ, and t_a, where a is a frictional constant, σ is the effective normal stress, and t_a the ``aftershock duration'', are simultaneously estimated. Simulations show that joint inversion of InSAR and seismicity data provides more reliable inversions than InSAR alone.
DE: 7280 Volcano seismology (8419)
DE: 8419 Volcano monitoring (7280)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005