HR: 16:45h
AN: S34B-04    [Abstracts]
TI: High-resolution P and S-wave Velocity Structures from Elastic Full Waveform Inversion of Multi-Component Ocean Bottom Cable Seismic Data
AU: Sears, T
EM: tjs54@cam.ac.uk
AF: University of Cambridge, Bullard Laboratories, Cambridge, CB3 0EZ, United Kingdom
AU: * Singh, S C
EM: singh@ipgp.jussieu.fr
AF: Institut de Physique de Globe de Paris, 4 Place Jussieu, Paris cedex 05, 75252, France
AU: Barton, P
EM: barton@esc.cam.ac.uk
AF: University of Cambridge, Bullard Laboratories, Cambridge, CB3 0EZ, United Kingdom
AB: Full waveform inversion is becoming a realistic option with the advent of modern computing facilities, both in global and exploration seismology. Over the last ten years, we have developed a series of elastic full waveform inversion algorithm and have applied to a variety of acquisition geometry. The forward modelling is based on the finite difference approximation to the full elastic wave equation in the time domain, which can incorporate converted waves, refraction, and attenuation. The inversion algorithm is based on the minimisation of observed data with synthetic data in a least-squares sense, and requires a cross-correlation of the back propagation of residual with forward propagated wavefield in a background media. Starting with the background velocity obtained using travel time inversion, we first invert wide-angle and low frequency data, which provides medium wavelength velocity structure, and then invert near offset and high frequencies that leads to high-resolution P- and S-wave velocity structure. We first invert vertical component data to obtain short wavelength P- and S-wave velocities, which are constrained by amplitude versus offset behaviour of the P-P reflection, and then invert horizontal component data to obtain very-high resolution S-wave velocity structure, which is constrained by P-S reflection. Finally, we invert all the data simultaneously to have consistency over the data and model space. We found that the high-resolution S-wave velocity image is far superior than the P-wave velocity image and provides information that may not be present in the P-wave velocity image. Combined P and S-wave velocity structure could be used to quantify sub-surface lithology and fluid saturation and pressure. In this presentation we will highlight the challenges faced during the development of our waveform inversion and their implication for the global seismology problems.
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: 2007 Fall Meeting