Time-lapse analysis is the process of acquiring and analyzing multiple geophysical (seismic, gravity, etc.) surveys, repeated at the same site over calendar time, in order to analyse differences between data sets from different times, especially useful in detecting fluid-flow/injection effects in a producing reservoir. If each survey is “3-D” then the resulting set of time-lapse data is often termed “4-D”, where the extra fourth dimension is calendar time.  Differences between data sets due to other sources such as variations in acquisition/processing parameters, tides, and background noise, must be removed or equalized prior to differencing.
- David E. Lumley, 2001, Time-lapse seismic reservoir monitoring, GEOPHYSICS, 66, NO. 1, P. 50–53.
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