P-Wave to Rayleigh-wave conversion coefficients for wedge corners; model experiments

An analytic solution is not available for the diffraction of elastic waves by wedges; however, numerical solutions of finite-difference type are available for selected wedge angles. The P - to Rayleigh-wave conversion coefficients at wedge tips have been measured on two-dimensional seismic models for stress-free wedges with wedge angles, θ 0 , of 10, 30, 60, 90 and 120°. The conversion coefficients show two broad peaks and a minimum as a function of the angle between the wedge face and the direction of the incident P -wave. The minimum occurs for the P wave incident parallel to the wedge face and one maximum is near an incidence angle of 90° to the wedge face. The amplitude of this maximum, relative to the other, decreases as the wedge angle increases. The asymmetry of the conversion coefficients, C PR ( θ ; θ 0 ), relative to parallel incidence ( θ = 0) increases as the wedge angle increases. The locations of the maxima and the minimum as well as the asymmetry can be explained qualitatively. The conversion coefficients are measured with an accuracy of ±5% in those regions where there are no interfering waves. A comparison of the data for the 10° wedge with the theoretical results for a half plane (0° wedge) shows good correlation.