The focusing analysis (FAN) approach developed by TGS uses demigrated time domain focusing operators to estimate anisotropic parameters for transversely isotropic media.

FAN leads to construction of the true focusing operator for migrated gathers. This begins with demigration of common image gathers to the time domain, then the focusing operator is calculated for various values of epsilon and delta from the zero-offset image or focal point, and finally these operators are scanned for the minimum objective function describing the difference between the calculated and true focusing operators. This method is fully automatic and can be used for any type of seismic acquisition.