Earthquakes occur when energy is released along faults in the earth. The focus is the point where the rock breaks along the fault, and the epicenter is the point directly above the focus on the surface. Seismic waves carry energy away from the focus, including P waves and S waves. P waves are compressional and can travel through solids, liquids, and gases. S waves are transverse shear waves that can only travel through solids. The largest earthquakes by magnitude include a 9.5 in Chile in 1960 and a 9.1 in Sumatra in 2004. Locating an earthquake's epicenter requires data from three seismic recording stations.

1. Earthquakes & Seismic
Waves

2. An Earthquake occurs when energy is
released through rapid movement along a
fault.

3. Current Earthquake Data
http://ds.iris.edu/seismon/

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.

6. Focal Depth
This is the distance between the Focus
and the Epicenter.

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.

13. Secondary Waves
S Waves can only travel through solids.

14. Surface Waves
Waves like L waves
and R waves travel
slightly slower then S
waves but do
tremendous damage.

15. https://www.youtub
e.com/watch?v=yO
GoKCK17a4

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.

21. https://www.youtub
e.com/watch?v=VS
gB1IWr6O4

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.

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”.

26. Tsunami

27. https://www.youtube.com/watch?annotatio
n_id=annotation_1885845763&feature=iv
&index=2&list=PLNspHwmzscYE2-
cUkOfHo92ATHZUqqsPH&src_vid=j0YOX
VlPUu4&v=pTtneXyhoPA