The velocity measurement limit in dynamic interferometry is ?Nyq, the velocity at which the interferogram is sampled at the Nyquist limit. We show that ?Nyq can be exceeded by assuming continuity of the surface motion and unwrapping the velocity modulo 2?Nyq. The technique was demonstrated in a high-speed speckle pattern interferometer with spatial phase stepping. Surface velocities of 4?Nyq were measured experimentally. With a reduced exposure, high-speed sub-Nyquist interferometry could be implemented up to a maximum acceleration of ?Nyq/ts, where ts is the detector frame period. © 2011 Optical Society of America.