Earthquakes
were seen on the ground, lines of sight and level distorted, and objects thrown upwards in the air.
Earthquakes are the result of a sudden movement of the earth. When this movement occurs, a tremendous amount of energy is released in the form of seismic waves. These waves travel both through the interior of the earth and along its surface. Seismologists are able to record an earthquakes exact location using seismographs across the globe. We are also able to use seismographs to help determine the magnitude of an earthquake, while interviews of people who witnessed or experienced the earthquake can help determine its intensity.
Additional Information
If you’d like some additional information, check out these web sites. The University of Nevada, Reno operates the Nevada Seismological Institute. They have some excellent information on earthquake Intensity including a complete list of the modified Mercalli intensity scale. They also have some great information on earthquake Magnitude, including a detailed description that includes many of the mathematical formulas for seismic moment and seismic energy. Also, check out the United States Geological Survey’s earthquake hazards program. The USGS site has up to date maps of earthquakes around the globe as well as information about earthquake hazards and preparedness. They also have some wonderful information that answers many of the questions children usually have about earthquakes.
Glossary
Body waves: Seismic waves that travel through the earth’s interior, radiating from the focus in all directions.
Epicenter: The area on the earth’s surface directly above the focus of an earthquake.
Focus: The point in the earth’s interior where the movement of an earthquake initially occurred.
Intensity: Measurement of the effect an earthquake has on people and property.
Magnitude: Measurement of the amount of energy released by an earthquake.
Modified Mercalli scale: Scale used to gage the intensity of an earthquake.
Moment Magnitude: Measurement of the amount of rock actually displaced by an earthquake and the surface are of the rupture.
P waves: Seismic waves that vibrate in the same direction that the waves are moving in.
Richter scale: Scale used by seismologists that reports an earthquakes magnitude.
S waves: Seismic waves that vibrate perpendicular to the direction the wave is traveling
Seismic waves: Waves of energy released when an earthquake occurs.
Surface waves: Seismic waves that travel along the surface moving away from the epicenter.
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