The geophysicist who interprets the seismic data generally ties the top picks and fault cuts that the geologist has made on the formations of interest to the seismic data. In that manner, The geophysicist will know, for example, that the strong reflector at 2.5 seconds corresponds to the Top of the Wilcox 'A' sand, at 2.51 seconds to the base of the Wilcox 'A' sand, and so forth. By following the seismic reflections, and recording the time values at a reasonable CDP or bin spacing on a map, the geophysicist can make maps of the subsurface. The geophysicist is actually mapping the two way time to a reflector- but these time maps can be converted to depth maps with adequate velocity information. Geophysicists also make synthetic seismograms from sonic logs, which turn a well log into a 'wiggle trace', that can more accurately tie into the seismic data.
The geophysicist will incorporate the faults that the geologist could interpret from the well logs, but she will also be able to see many more faults on the seismic data that could not be determined by the log data. The first step in constructing a map of a given surface, called a 'horizon' by the geophysicist, is usually to tie all of the faults together for that surface, before interpreting the horizon. Log data, no matter how dense the well coverage is, cannot provide the amount of data samples that seismic data can provide. In addition, with some geological environments and special processing techniques, hydrocarbons may be directly observed on the seismic data. Locations for drilling wells are generally based on the seismic interpretation. In the past ten years, workstations have made a major difference in the way geophysicists interprets data. In addition, advances in acquisition and processing have made advances in the quality of the data. As a result, far more information is extractable from the data than ever before. Mapping the characteristics of the seismic data such as amplitude is now commonplace, and could not be done before workstations arrived on the scene.