Rapid 3D Refraction And Reflection Raytracing

We present a rapid 3D raytracing method optimized for the computation of reflection and refraction<br>wavefronts from a point source in a class of simplified models. The models consist of constant<br>velocity layers separated by arbitrary (and possibly complex) interfaces. We demonstrate that the<br>method simulates wave phenomena such as diffraction and head wave propagation. The approach<br>is extremely fast since it avoids traveltime expansion in the volume between interfaces, and solves<br>a simple 2D problem on each interface. Other methods require local propagators (even in constant<br>velocity regions) whereas our approach enables large jumps of wavefronts from interface to interface.<br>From interface to interface for reflection/transmission or on the same interface for refraction calculation,<br>graph theory and Snell’s law are applied to optimize raytracing. The calculation of raypaths<br>for an actual 3D survey in the Wind River Basin with 1690 sources (700,000 source-receiver pairs)<br>and a velocity model with two complex interfaces required less than 12 minutes of CPU time on<br>a 150 MHz Silicon Graphic 02 workstation. The computation time scales approximately linearly<br>with the number of interfaces.