Abstract
We present a method for determining the specific quality factor Q (super -1) by the use of spectral ratios of seismic refraction data. The only modifications to standard refraction profiles are that the source and receivers be sufficiently far away from reflective boundaries to eliminate the angular dependence of the source spectrum itself and of the observation of the source signal by the receiver. The last requirement may not be too significant. Application of this method for determining attenuation as a function of depth was applied to data obtained in a thick sedimentary section in the Bay of Bengal. Once an adequate velocity-depth function is determined, attenuation as a function of depth is readily calculated by the use of linear inverse theory. Several preferred solutions are discussed, including a model of constant Q (super -1) of 0.0115. A comparison of our data with a compilation of data from the published literature of attenuation with depth reveals a reasonable concordance, but with some slight differences. A peak of attenuation at 600-m depth probably represents the depth of lithification of the sediments into mudstone.
