Inversion of Scattered Waves for Material Properties in Fractured Rock

摘要

The authors apply a recently developed low-frequency, non-linear inversion method211u001ewhich includes near and far field terms to a crosshole data set to determine the 211u001ebulk and shear modulus, as well as the density for a fractured zone in a granitic 211u001erock mass. The method uses the scattered elastic wavefield which is extracted 211u001efrom the recorded data before the inversion is performed. The inversion result is 211u001eappraised by investigating the resolution and standard deviation of the model 211u001eestimates. The sensitivity of the three parameters to different features of the 211u001emedium is revealed. While the bulk modulus appears to be sensitive to voids and 211u001ewelded contacts, the density is mostly affected by fractured zones. The shear 211u001emodulus is least constrained due to the absence of S wave anisotropy information. 211u001eIt is shown that the three medium parameters are generally sensitive to other 211u001emedium features than those determined by velocity inversions. Thus this method is 211u001eviewed as a complimentary approach to travel time tomography which provides more 211u001einsight into the material properties of inhomogeneous media.