TWO TYPES OF SEISMIC WAVES

P OR COMPRESSIONAL WAVES - VOLUME CHANGES

MATERIAL COMPRESSED OR EXPANDED IN DIRECTION WAVE PROPAGATES

(USGS)

S OR SHEAR WAVES - DISTORTION WITHOUT VOLUME CHANGES -

MATERIAL SHEARED IN DIRECTION NORMAL TO WAVE PROPAGATES

P WAVES TRAVEL FASTER (ABOUT 1.7X) THAN S WAVES