Earthquakes Lakeland Central School District地震湖区中心学区.pptVIP

Earthquakes A whole lotta shakin’ goin’ on. Focus Point at which there is a sudden release of energy below Earth’s surface usually along a fault. Epicenter Point on Earth’s surface directly above the focus. Elastic Rebound Stress builds along fault until the friction that holds the fault together is overcome. The fault slips. The deformed rocks snaps back. Earthquake Waves P-waves are push-pull waves. Compress at the front and expand at the rear. This vibration goes in the same direction that the wave is traveling. P-waves are the fastest waves. Earthquake Waves S-waves vibrate a right angles to the direction of travel. S-waves are slower than P-waves. Measuring Earthquake Strength A seismograph measures and records an earthquake’s duration and magnitude. The Richter scale is a logarithmic scale. Earth’s Interior P and S waves give us clues to the Earths interior. That no direct S waves reach the far side shows that the Earths outer core is liquid. The size of this S-wave shadow tells us the size of the core. * *