(dub’ lit) 1. Two closely spaced peaks on a seismic trace, between which the trace does not cross the zero-amplitude axis. 2. A two-stick wavelet [a,b], whose z-transform is a+bz. If |a|>|b|, [a,b] is minimum phase; if |a|<|b|, maximum phase. Sometimes called a dipole. 3. See doublet modulation. 4. The first derivative of the Dirac delta function.