Presentation on theme: "Earthquakes. Earthquakes Result from Stress What is an Earthquake? –Definition : Shaking of a crust by a release of energy – Results : 1. Explosions,"— Presentation transcript:
Earthquakes Result from Stress What is an Earthquake? –Definition : Shaking of a crust by a release of energy – Results : 1. Explosions, fires, broken sewage lines and water mains. Unstable roads, railroads, runways. 2. Tsunamis
Tsunami: Giant ocean wave generated by an earthquake whose epicenter is on the ocean floor. (computer generated photo)
Causes of Earthquakes Elastic – rebound theory –Definition : When stress overcomes friction, sudden movement occurs and a snap forward occurs. This is followed by a rebound or snap back.
Magnitude vs. Intensity Magnitude –Definition: The amount of energy released by an earthquake. Intensity –Definition: The amount of damage caused by an earthquake. Intensity: Mercalli Scale Magnitude: Richter Scale - -Scale 1- 12 - Scale 1- 10 1= no damage 30 times more energy as you 12= total destruction go up the scale
Earthquake Waves Kinds of wave motions –P Waves Primary (compressional) waves Can travel through any materials (solid, liquid, gas) Back and forth waves Twice as fast as S waves –S Waves Secondary waves Side to side waves Can travel through solids only –L Waves Surface waves Slowest moving waves Cause the most damage
Seismograph: Instrument used to detect and record vibrations from earthquakes.
Seismogram: Record of an event from seismograph
Lag Time: Since P waves travel faster than S waves, scientists determine distance to the epicenter by analyzing the difference in arrival times.
Lag Time: The longer the lag time between the arrival of the P-waves and the arrival of the S-waves, the farther away the earthquake occurred.
Locating the epicenter Triangulate between 3 or more seismograph stations Where the circles Intersect = an epicenter