The travel velocity of these two wave types is not the same (P-waves are faster than S-waves). Thus, if there is an earthquake somewhere, the first waves that arrive are P-waves. In essence, the gap in P-wave and S-wave arrival gives a first estimate of the distance to the earthquake.
With the mysterious U.S. Senator Eddie Morra (Bradley Cooper) providing him with a second drug to counteract NZT's deadly side effects, Brian uses his enhanced abilities to help FBI agent Rebecca Harris (Jennifer Carpenter).
Callies is returning as Sara Tancredi, the prison doctor-turned-love interest for Miller's Scofield, and the mother of Michael's son. Nolasco played Fernando Scure, Michael's cell-mate at Fox River State Penitentiary who helped Sara escape from prison in the series finale.