Why do P waves arrive first?
When an earthquake occurs, seismic waves, including P and S waves carry energy away from the hypocenter in all directions. The P wave propagates with a velocity of about six kilometers per second in rock, while the S wave is slower at four kilometers per second. This video explores how this difference wave speeds results in staggered arrivals that, in turn, provides information about how far away the earthquake was from the seismograph.
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