North-south line (inline) 22 showing location of 9-C VSP well. The reflector at the top of the gas producing interval, a red trough at 1.28 s, marks the change from the low-velocity Waltman Shale to the high-velocity LFU. (a) The east-west azimuth source-receiver data volume shows a bright Top LFU reflector package, while (b) the north-south azimuth source -receiver data volume shows dim Top LFU reflectors.