Fault Mapping

Gasch & Associates of Rancho Cordova, California, wanted to constrain the location and down-dip geometry of a fault in southern California. The only data input used to produce the velocity model was the first arrival travel-time data, and array geometry. No other a priori data were used.

This is a velocity model from one of the lines. As you can see, SeisOpt® @2D handles strong lateral variations in velocity and elevations quite well. In fact, the petroleum uses our software for near-surface velocity static corrections because of the detail in which near-surface velocities are revealed. The fault is clearly shown at about offset 420 feet. SeisOpt® @2D is able to model vertical and near-vertical features because it does not make any assumptions on the orientation of the velocity gradient. The velocity model also picked up some subtle lateral velocity features adjacent to the fault.

SeisOpt® @2D let's you know if your target has been properly sampled prior to leaving the field, which can save enormous amounts of time and money. It produces a hit count plot that shows you how many rays have sampled each discrete point within your study area. If you look at some of the other examples at our site, you will also see how SeisOpt® @2D can either interactively or automatically optimize your seismic data acquisition array to be sure your target is properly sampled prior to leaving the field. In this example, notice the behavior of the rays in the vicinity of a steeply dipping high velocity layer, in this case, the fault. Observing the way the rays are behaving below your feet, while you are still in the field is useful to plan out your survey to effectively sample your target.

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