1. Earthquakes

2. What are Earthquakes?
Earthquake - sudden movement of the ground caused by the release of energy when the rocks move along a fault.
Fault - a break in rock where movement occurs.

3. Where do most earthquakes occur?
Most earthquakes occur at plate boundaries, where there is a lot of stress.
Some happen at fault zones

4. Anatomy of an earthquake

5. Anatomy of an Earthquake
Focus - where the first movement occurs in the earth’s crust.
Epicenter - point on the earth’s surface where the earthquake is felt first.

6. Seismic Waves Body waves - travel thru the earth’s interior. Includes:
P waves - primary
Fastest waves, first to be detected.
Move back and forth parallel to the motion of the wave.
Move thru solids, liquids and gases.
S waves - secondary
Second fastest
Move perpendicular to motion of wave.
Move only thru solids

7. Seismic Waves Surface waves - travel along the earth’s surface.
Slowest moving waves
Move rock side to side and up and down
Cause the most damage during earthquakes

9. Shadow Zones

10. Seismology Seismology is the study of earthquakes.
Seismograph - instrument that records seismic waves.

11. Earthquake Scales Mercalli Scale Richter Scale
a seismic scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake, and is distinct from the moment magnitude usually reported for an earthquake (sometimes misreported as the Richter magnitude), which is a measure of the energy released
a numerical scale for expressing the magnitude of an earthquake on the basis of seismograph oscillations.

12. Measuring Earthquakes
Magnitude - strength of an earthquake.
Richter scale
Intensity - how much damage an earthquake causes.
Mercalli scale