INVERSION OF SEISMIC ATTRIBUTES FOR VELOCITY AND ATTENUATION STRUCTURE

We have developed an inversion formulation for velocity and attenuatio n structure using seismic attributes, including envelope amplitude, in stantaneous frequency and arrival times of selected seismic phases. We refer to this approach as AFT inversion for amplitude, (instantaneous ) frequency and time. Complex trace analysis is used to extract the di fferent seismic attributes. The instantaneous frequency data are conve rted to t using a matching procedure that approximately removes the e ffects of the source spectra. To invert for structure, ray-perturbatio n methods are used to compute the sensitivity of the seismic attribute s to variations in the model. An iterative inversion procedure is then performed from smooth to less smooth models that progressively incorp orates the shorter-wavelength components of the model. To illustrate t he method, seismic attributes are extracted from seismic-refraction da ta of the Ouachita PASSCAL experiment and used to invert for shallow c rustal velocity and attenuation structure. Although amplitude data are sensitive to model roughness, the inverted velocity and attenuation m odels were required by the data to maintain a relatively smooth charac ter. The amplitude and t data were needed, along with the traveltimes , at each step of the inversion in order to fit all the seismic attrib utes at the final iteration.