1. Earthquakes

3. An earthquake is a shaking of Earth’s crust caused by a release of energy. Earthquakes are often more destructive than volcanoes because the area affected can be greater.

4. Earthquakes More than 1 million earthquakes occur each year – that’s about 1 every 30 seconds.

5. Death Tolls YearLocationDeaths 1960Agadir, Moroco12 000 1962Northwestern Iran12 230 1968Northeastern Iran12 000 1970Northern Peru66 974 1976Guatemala22 778 1976Tangshan, China800 000 1978Northeastern Iran25 000 2008China~70 000 (another ~18 000 missing) 2010Haiti~50 000 (est.)

6. Causes of Earthquakes The major cause of earthquakes is when stress builds up within Earth’s crust. This stress occurs when plates move past each other.

7. Normal Faults

8. Reverse Faults

9. Strike-slip Faults

10. How Deep? Most earthquakes occur between 30-700 km below the surface. The type of plate boundary involved will determine the depth of the earthquake.

11. How Deep? Focus: The place inside the Earth where the earthquake actually occurs. Epicenter: The point on Earth’s surface directly above the focus.

13. Earthquake Waves 1.Body Waves: Primary or P-waves Secondary or S-waves 2.Surface Waves: L-waves

14. Body Waves Travel through the body of the Earth. P-waves: –Move back and forth (compression). –Can travel through any material. Solid rock, magma, water, air.

15. Body Waves S-waves: –Move up and down. –Are almost twice as slow as P-waves. –Cannot travel through liquids.

17. Surface Waves When P and S waves reach the surface, they create an L-wave. They resemble ripples on a pond and can travel about 3 km/h.

18. Surface Waves

21. Seismographs The instrument used to record earthquake waves is called a seismograph. A seismogram is the data recorded from the seismograph.

23. Measuring an Earthquake

24. Earthquake Magnitude The scale used for earthquake magnitude is the Richter Scale. The Richter Scale measures the amount of energy released by an earthquake.

26. Magnitude 6.0