Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release...
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![Page 1: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/1.jpg)
Earthquakes
![Page 2: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/2.jpg)
Earthquake Terms• An earthquake is a trembling of the
Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon these are called moonquakes).
• Earthquake activity is also referred to as seismic activity.
• The energy is generally released along fault lines as sections of ground move.
![Page 3: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/3.jpg)
Earthquake Terms
• The point of energy release is called the focus. The point on the Earth directly above the focus is called the epicenter.
• Surface waves move along the surface of the Earth while body waves penetrate the Earth’s interior. Surface waves cause most of the structural damage.
![Page 4: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/4.jpg)
Waves
• The types and sizes of waves generated by an energy release can provide information about the location of the quake and the magnitude.
• Earthquakes are recorded by an instrument known as a seismograph.
![Page 5: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/5.jpg)
Types of Waves
• Primary or P-waves – cause compression and dilation along axis of propagation
![Page 6: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/6.jpg)
Types of Waves• Shear or S-waves – cause vertical
motion along axis of propagation
![Page 7: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/7.jpg)
Seismographs• P-waves travel faster than S-waves.
![Page 8: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/8.jpg)
Seismographs
• The time between the arrival of the P wave and S-wave is the S-P time interval. It is related to the distance of the detecting device from the epicenter.
![Page 9: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/9.jpg)
S-P Interval
If you know the S-P interval you can determine the distance from the recording station to the epicenter.
![Page 10: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/10.jpg)
When you find the distance from the epicenter for 3 stations, you can pinpoint the epicenter. You draw a circle from each station with a radius that is the distance to the epicenter for each station. Where the 3 circles intersect is the epicenter.
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Magnitude• To determine the magnitude of an
earthquake you need the distance to the epicenter and the strength (amplitude) of the S-wave from the seismogram.
![Page 12: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/12.jpg)
MagnitudeFor any seismic station, the distance to the epicenter and the amplitude of the S-wave will estimate the magnitude.
Using the nomogram shown here, draw a line connecting the distance and amplitude for a the station. Where the line crosses the magnitude scale is the approximate magnitude.
For a distance of 220 miles and an amplitude of 50 mm, the magnitude is 5.3.
![Page 13: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/13.jpg)
Magnitude and the Richter Scale
![Page 14: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/14.jpg)
![Page 15: Earthquakes. Earthquake Terms An earthquake is a trembling of the Earth caused by a sudden release of energy stored in subsurface rock units (on the Moon.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649de55503460f94addf04/html5/thumbnails/15.jpg)
Now…
• Back to the “Shake, Rattle, and Roll” activity and locate an earthquake yourself!