Term
| What causes an earthquake ? |
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Definition
| Earthquakes are caused by the vibrations of Earth produced by the sudden release of energy |
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Term
| Describe the location of an epicenter and focus. |
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Definition
Epicenter is the location of the surface of Earth directly above the focus.
Focus is the point within the Earth where the earthquake starts. |
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Term
| What is the elastic Rebound hypothesis ? How does it relate to earthquakes ? |
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Definition
| Elastic rebound hypothesis is the release of built-up energy. Most earthquakes are produces by the release of elastic of elastic energy stored in rocks that has been subjected to great forces. |
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Term
| Describe aftershocks and foreshocks. |
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Definition
Aftershocks are small quakes that come after a major earthquake.
Forceshocks are small quakes that come before a major earthquake. |
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Term
| How are earthquakes measured ? |
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Definition
| Historically, scientists have used two different types of measurement to describe the size of an earthquake--intensity and magnitude. |
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Term
| Describe the following earthquake waves: surface, S waves, and P waves. |
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Definition
Surface waves=seismic waves that travel along earth's outer layers. They move up, down, and side to side. Most destructive earthquake wave. Last to arrive at the seismograph
S waves=shake particles at right angles to their direction of travel. Also known as traverse waves. Can only travel though solids. Slower than P waves but faster then surface waves.
P waves=They push ( compress ) and pull ( expand ) rocks in the direction the wave travels. Also known as compression waves. Can travel through solids, liquids & gas. Fastest waves (arrive 1st to the seismograph)
The order would be P,S,Surface. |
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Term
| How do scientist locate earthquakes? |
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Definition
(distance and directions)
The difference in velocities of P waves provides a way to locate the epicenter. Scientists use a travel-time graph, in which one needs at least 3 seismograph station data. |
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Term
| Where do most earthquakes occur ? |
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Definition
| Most of these earthquakes occur around the outer edge of the Pacific Ocean. This zone is known as the circum-Pacific belt. Active earthquake area in this zone include Japan, the Phillipiness, chile, and Alaska's Aelutian Islands. |
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Term
| Describe each of the different scale used to measure earthquakes. Which one measures intensity and which one measures magnitude? What is the difference between magnitude and intensity ? |
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Definition
| Richter Scale=measures the magnitude of an earthquake. Based on the amplitude of the largest seismic wave. A ten fold system. News reporters use this scale, but scientists no longer use this scale. |
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