IMAGING BENEATH A HIGH-VELOCITY LAYER USING CONVERTED WAVES

High-velocity layers (HVLs) often hinder seismic imaging of deeper reflectors using conventional techniques. A major factor is often the unusual energy partitioning of waves incident at an HVL boundary from lower-velocity material. Using elastic physical modeling, I demonstrate that one effect of this factor is to limit the range of dips beneath an HVL that can be imaged using unconverted P-wave arrivals. At the same time, however, partitioning may also result in P-waves outside the HVL coupling efficiently with S-waves inside. By exploiting some of the waves that convert upon transmission into and/or out of the physical-model HVL, I am able to image a much broader range of underlying dips. This is accomplished by acoustic migration tailored (via the migration velocities used) for selected families of converted-wave arrivals.