1. Earthquakes & Seismic Waves

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

3. Current Earthquake Data

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.

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, Chile 9.5
March 28th, Alaska 9.2
December 26th, Sumatra (Ocean) 9.1
March 11th, Japan (Ocean) 9.0
February 27th, Chile 8.8
Largest In Destruction
Date Location Deaths Magnitude
Jan 25th, China 830,000 8
July 27th, China 655,
Aug. 9th, Syria 230,000 Unknown
Dec. 26th, Sumatra 227,
Jan. 12th, Haiti 222,

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