HR: 0800h
AN: G21A-0101    [Abstracts]
TI: A Comparison of Geodetic Strain Rates With Earthquake Moment Tensors
AU: * Zhu, W
EM: zwei@ic.sunysb.edu
AF: Wei Zhu, Geosciences Department, State University of New York at Stony Brook, Stony Brook, NY 11794 United States
AU: Holt, W E
EM: wholt@mantle.geo.sunysb.edu
AF: Wei Zhu, Geosciences Department, State University of New York at Stony Brook, Stony Brook, NY 11794 United States
AB: In this paper we compare the global model from interpolation of GPS data with the global model inferred from earthquake moment tensors. We use the Harvard CMT catalog to calculate moment rates based on 3 assumptions: a. we assume earthquakes are self-similar; b. we assume a uniform Beta value of the Gutenberg-Richter distribution; c. we assume that all of the long-term strain is accommodated seismically. If these assumptions are correct then the seismicity rate is proportional to the tectonic moment rate. We then inferred a long-term moment rate tensor field estimate for all plate boundary zones from which we inferred a long-term seismic strain rate estimate. Using this estimate we solved for a self-consistent kinematic global solution (motions of rigid spherical caps and motions within plate boundary zones) using bi-cubic spline interpolation of the inferred strain rates. We tested the above assumptions by comparing the global kinematic model obtained from earthquake data with a global model inferred from interpolation of space geodetic data [Kreemer et al., 2003]. A comparison between the two models shows good agreement for motion directions of the North American, and Eurasian plates and for the plate boundary zones within these regions (e.g., Tibet). Problems arise, and our assumptions break down, for plates adjacent to fast spreading ridges where divergence of plates appears to be accommodated aseismically. We next investigated the correlation of strain rate tensor inferred from the interpolation of GPS observations within deforming Asia with the earthquake moment tensors, using both elastic and viscous rheologies. Our solutions satisfy the force balance equations for a given rheology. Our goal for this exercise is to investigate whether the interseismic signal, inferred from GPS, correlates better with moment tensor style for an elastic rheology as opposed to a viscous rheology. Results to date suggest that the viscous models only provide a better agreement with observed styles of faulting if the relationship between stress and strain rate is anisotropic.
DE: 9320 Asia
DE: 7230 Seismicity and seismotectonics
DE: 8123 Dynamics, seismotectonics
DE: 7209 Earthquake dynamics and mechanics
DE: 1236 Rheology of the lithosphere and mantle (8160)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting