  The hypocentral depth is a key requirement in seismology and earthquake
engineering, but it is very difficult to be determined. The current accepted
improvement is taking advantage of the depth phases, such as the pP, to
constrain this parameter. However, it is not easy to pick such a phase in a
seismogram from the other phases and the backgound noises. Here we propose the
use of the minimum entropy deconvolution (MED) to detect it. Synthetic tests
show that impulse(s) hidden in the seimic noises, eg. discrete unit impulses or
the Gaussian mono impulses, can be detected completely. Further, we assume that
the pP phase is an impulse-like signal buried in the Z component of the
seismogram and applied this technique to 12 earthquakes in the International
Association of Seismology and Physics (IASPEI) Ground Truth (GT) reference
events list. Results show that 9 out of 12 earthquakes have absolute errors of
less than 2.00 s for the travel-time differences of pP-P, and the maximum
absolute error is 3.06 s . This demonstrate that the assumption above is
reasonable, and this technique works well and effectively even for a single
seismogram. Due to its little cost and effectiveness, this technique may be
also useful in the starting points for other methods to detect pP phase.
