It just likes below
[zhongen@localhost gmtplot]$ gmt makecpt -Cpolar -T3/4/0.3 -I -Z > seis.cpt
makecpt: Error: CPT polar.cpt has no z-slices!
[Session gmt (0)]: Error returned from GMT API: GMT_CPT_READ_ERROR (8)
[Session gmt (0)]: Error returned from GMT API: GMT_CPT_READ_ERROR (8)
[Session gmt (0)]: Error returned from GMT API: GMT_CPT_READ_ERROR (8)