Application Of Two-Pass Migration To 3D Gpr Data

Two-pass migration refers to the method of migrating a three-dimensional data set using only 2D<br>migration routines. The data are migrated twice; once each along two orthogonal axes. The method is easily<br>implemented with any 2D migration code, and in the case of Kirchhoff migration, is far less computationally<br>expensive than one-pass 3D migration. As computing power continues to increase, this savings in<br>computation cost becomes less relevant. However, we maintain that the method, primarily due to<br>availability of 2D migration codes and ease of implementation, holds significant utility in shallow<br>geophysics, and ground-penetrating radar in particular. We review two-pass migration through simple<br>synthetic examples and demonstrate that for a constant velocity medium, it is equivalent to full 3D<br>migration. Then, through a series of test pit studies and a field example, we demonstrate that the method<br>provides results comparable to one-pass 3D migration for a variety of applications and velocity profiles<br>typical of GPR imaging problems.