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).
Darabont is seeking to recapture the spirit of Frank Capra - with Carrey in the role of a James Stewart or Gary Cooper. Yet even though Darabont shares Capra's dewy-eyed optimism, his film's sluggish pace means he lacks Capra's screwball zest.