Abstract We measured time differences between P-wave arrivals and the times at which squared amplitudes of high bandpass (2–4 Hz) filtered P-waves became the largest for large shallow earthquakes that occurred during the period 1995–2007. The time differences were then normalized by twice the centroid time shift for the corresponding earthquakes. We found that most of the seismograms had normalized time differences that congregated at about 50% (corresponding to centroid time shifts). Few normalized time differences were found in the 0–20% range. These results support the use of this time difference to infer the order of the source duration and, thereby, the effectiveness of the duration measurement procedure of the high-frequency energy radiation that we recently developed.