HR: 09:25h
AN: T31D-06    [Abstracts]
TI: Tomographic inversion of amplitudes and phases of Rayleigh waves with 2-D sensitivity kernels applied to southern California
AU: * Yang, Y
EM: Yingjie_Yang@brown.edu
AF: Yingjie Yang, 324 Brook street Geology Dept. Box 1846 Brown University, Providence, Ri 02912 United States
AB: We use 2-D sensitivity kernels for fundamental-mode Rayleigh waves based on single-scattering (Born) approximation to calculate the effects of heterogeneous structure on wave field in a regional surface wave study. The calculated phase and amplitude data using the 2-D sensitivity kernels are compared to phase and amplitude data obtained from synthesized seismic waveforms modeled by pseudo-spectral method for a plane Rayleigh wave propagating over heterogeneous structure. The kernels can accurately predict the variation of the wavefield caused by the heterogeneous structure. An inversion method based on the sensitivity kernels is developed and applied to synthesized cases. The method can almost completely recover anomalies within an array of stations when the size of anomalies is larger than one wavelength of surface waves. The new method is also used to invert for phase velocities in southern California with Rayleigh waves recorded at the Trinet network at periods from 25 to 143 s. The new method has much higher resolution compared to our previous method that uses a Gaussian function with same characteristic length along ray path to represent sensitivity, and the inversion yields about 15 percent variation reduction for short periods. New phase velocity images show larger anomalies in amplitude with high velocity along the coast area in southern California, a low velocity anomaly in Western Basin and Range and a high velocity anomaly beneath Peninsular Range. The well-known high velocity anomaly associated with Transverse Range is also clearly imaged, which can be seen at periods up to 83 s in the eastern Transverse Range. The new methods can also retrieve attenuation structure and station site responses, which will be incorporated as additional information with 2-D phase velocity to better constrain shear velocity beneath southern California.
DE: 8180 Tomography
DE: 7255 Surface waves and free oscillations
DE: 7218 Lithosphere and upper mantle
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting