Measuring Earthquakes

Cornell Notes page 127

What is seismology?

• The study of earthquakes

• An entire branch of science is devoted to understanding earthquakes

What do we use to measure

earthquakes?

• an instrument that measures vibrations in the ground, and records the location and strength of an earthquake

Seismograph

An alternative seismic instrument…

What is the Richter Scale?

• Measures the magnitude or strength of the shock waves.

• Is measured in steps from one upward.

• Each successive unit is ten times more powerful than the one before.

• A 7.0 on the Richter scale is 1000 times more powerful than an earthquake measuring 4.0.

What is the Mercalli Intensity Scale?

• Measures what is felt by people and the amount of damage caused

• Uses roman numerals

• Scale: I- not felt to XII- total destruction

Scale II

• Felt indoors by few

Scale IV

• Felt indoors by many, outdoors by few

Scale VI

• Felt by all, indoors and outdoors. Moved furniture

Scale VIII

• Fright general - alarm approaches panic.

Scale XII

• Damage total - practically all buildings damaged greatly

http://www.abag.ca.gov/bayarea/eqmaps/doc/mmi.html