ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

1aAO12. Shear wave attenuation estimates from inversion of Scholte wave data.

Hassan B. Ali

Michael K. Broadhead

Code 7173, Naval Res. Lab., Stennis Space Center, MS 39529-5004

On the basis of the correlation between sediment stratigraphy and modal dispersion, inversion of Scholte wave data allows one to estimate the shear wave velocities within the sediments. In some cases, this may be a sufficient characterization of the sediments. However, shear velocities contain only part of the wave information, and this will not generally suffice for recovery of the full measured time series. In realistic sediments, a propagating pulse will also be affected by the attenuation profile of the medium. Moreover, the amplitudes of the constituent frequencies will generally be attenuated differently, resulting in distortion of the pulse. Using the results of recent deep-water measurements, examples are presented of the relationship between sediment stratigraphy and Scholte wave modal dispersion. The modeling is then extended to examination of seismogram parameters, using iterative analysis of the shear attenuation profiles and exploitation of the spectral properties of the time series. It is shown that the shear Q profile is crucial in achieving an adequate match to the measured data, but some degree of nonuniqueness is possible. [Work supported by Office of Naval Res., Prog. Element No. 0601153N, with technical management provided by the Naval Res. Lab.]