1. Scales used to measure earthquakes

2. Richter scale
Uses the distance from epicenter and largest amplitude from the seismogram.
Scales ranges from Each increase is 10X greater than the previous.

4. Moment Magnitude scale
Estimates the total energy released by measuring the movement along the fault, the area of the break, & the strength of the rock type.
Scale ranges from Each increase is 10X greater than the previous.
This scale is most widely used by scientists.

5. Comparing Richter to Moment Magnitude
Earthquake Yr Richter MMS
New Madrid, MO
San Francisco, CA
Prince William, AK
Northridge, CA
Port-Au-Prince, Haiti
Maule,Chile

6. Mercalli Scale Measures intensity not magnitude.
Intensity measures the amount of shaking based on the amount of damage (effects on people, buildings, and the land surface in an area).
Intensities typically increase close to an earthquake's epicenter.
Intensity ratings are expressed as Roman numerals between I at the low end and XII at the high end.

7. This map plots the Mercalli Intensity ratings of localities near the Oct. 17, 1989 Loma Prieta (World Series) earthquake.
Note the locations of unusually high intensities (up to IX) far north of the earthquake's epicenter, near San Francisco Bay.
Why is the intensity higher further from the epicenter?

8. Chilean
Intensity Map
Haitian
Intensity Map