3. • An Earthquake occurs when energy is released
through rapid movement along a fault.
• An EARTHQUAKES are natural geological
phenomena caused by the sudden and rapid
movement of large volume of rocks.
4. Focus
• That is the point along the fault line where the
rock under stress breaks.
5. Epicenter
• Is the point on the earth’s surface directly above
the Focus.
7. Seismic Waves
• Energy from an Earthquake is carried away
from the focus as Seismic Waves.
• There are many different types of waves.
• We will concentrate on the two most
prominent.
8. Primary Waves
• P Waves
• The fastest seismic wave.
• Arrives at recording stations first (Primary).
9. Primary Waves
• P waves are compressional waves.
• The energy travels in the same direction as the
wave travels.
10. Primary Waves
• P waves can travel through solids, liquids or
gases.
11. Secondary Waves
• S Waves
• Arrives at recording stations second
(secondary).
12. Secondary Waves
• S waves are transverse waves.
• Another term is shear waves.
• The energy is perpendicular to the direction of
wave travel.
16. Seismograph
• Instruments that detect and measure seismic waves
are called Seismographs.
• They originally were a weight and pen suspended
over a moving drum.
17. Seismograph
• The tracing on the drum is called a seismogram.
• The different types of waves make different
tracings on the seismogram.
22. History of Earthquakes
Largest In Magnitude
• Date Location Magnitude
• May 22nd, 1960 Chile 9.5
• March 28th, 1964 Alaska 9.2
• December 26th, 2004 Sumatra (Ocean) 9.1
• March 11th, 2011 Japan (Ocean) 9.0
• February 27th, 2010 Chile 8.8
Largest In Destruction
• Date Location Deaths Magnitude
• Jan 25th, 1556 China 830,000 8
• July 27th, 1976 China 655,000 7.5
• Aug. 9th, 1138 Syria 230,000 Unknown
• Dec. 26th, 2004 Sumatra 227,898 9.1
• Jan. 12th, 2010 Haiti 222,570 7.0
23. Locating an Earthquake Epicenter…
• To find where the an
Earthquake originates you
need wave data from 3
recording stations.
• Circles are drawn around
these stations.
• Where the 3 circles
connect is where the
earthquake originated.
24.
25. Underwater E-quake
• Fault movement along the ocean floor moves
the water up and down which can create a
massive wave called a “Tsunami”.
