Abstract:
The vertical distribution of the scattering properties of the lithosphere can be found using Bocharov's formula which describes the broadening of an incoherent pulse with distance as it propagates in a scattering medium with scattering varying along the raypath. For a piecewise constant scattering distribution, Bocharov’s formula yields a linear equation for every raypath that relates the scattering of the blocks traversed by the raypath to a parameter that defines the pulse width. This set of equations can be solved by least squares to find scattering distribution in a certain lithospheric volume. Records of P and S waves from local earthquakes with focal depths of up to 140 km made at six Kamchatkan stations were measured to determine the onset-to-peak delay times (400-600 measurements). These data were inverted for each station to find scattering for a layer-on-half-space model. The results did not differ much between the stations and yielded the following distribution: scattering was 0.02 1/km (P waves) and 0.008 1/km (S waves) in the upper layer 30-50 km thick and 5-10 times as low in the lower layer ((30…50)-140 km). The exact scattering of the lower layer was not evaluated.
