DEK: this is the standard Harvard format (read the full description). It includes both initial hypocenter location (taken from NEIC bulletins) and all parameters calculated in the inversion: centroid coordinates and depth, moment tensor elements, best-fitting double couple.
NDEC: this is the more recent between the standard Global CMT formats (read the full description). It includes both initial hypocenter location (taken from NEIC bulletins) and all parameters calculated in the inversion: centroid coordinates and depth, moment tensor elements, best-fitting double couple.
psvelomeca: this data line includes centroid coordinates, strike, dip and slip of each focal plane and the seismic moment. It is useful when using the psvelomeca plotting command in the old GMT graphics package. It can be also used with the psmeca command of more recent version of GMT graphics package, adding the -o option.
PSMECA: this is the data line to use with the more recent versions of GMT graphics package, where the instruction psmeca allows to map the moment tensor (non-double couple component).