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10.1 Shot Record Modeling     continued...

These geometry considerations are not as critical in seismic modeling because the physical field constraints do not apply. The amount of data generated by a seismic model can be a problem, and it is not always wise to record every grid point along the receiver line for every time step. Sufficient data must be recorded to prevent aliasing the data [19]; the Nyquist limit is two grid points per wave length. Care must be taken to collect data which is not aliased either in space or time. While two grid points per wavelength is the theoretical limit, careful experimenters use at least three.

The routine seismic processing sequence will attempt to flatten the time recordings and sum into a stack section. This stacking process reduces the amount of data by a significant amount. The individual shot records are corrected for offset, the distance from the source location, and then summed. This process is termed a moveout correction. The equivalent seismic process would be to use only one receiver for every shot point location and record this data. This coincident source and receiver position is known as zero-offset data and would not need moveout correction.