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Wave Scales Pg. 62
Seismic waves Pg. 63

2. Seismic Waves Pg. 63 Body waves-travel through the earth’s interior.
1. P waves(primary) -Fastest waves, first to be detected.
Move back and forth parallel to the motion of the wave.
Move through solids, liquids and gases.

4. 2. S waves(secondary) - Second fastest
Move perpendicular to motion of wave.
Move only through solids

6. Surface waves-travel along the earth’s surface and move the slowest.
Cause the most damage during earthquakes
1.Rayleigh wave(P) - Move rock up and down
2.Love wave(S) – Move rock side to side

7. Rayleigh Wave

8. Love wave

9. Shadow zone – area on Earth’s surface where no seismic waves from a particular earthquake can be detected.

11. Seismology Seismology is the study of earthquakes.
Seismograph-instrument that records seismic waves.

13. Measuring Earthquakes
Magnitude-strength of an earthquake.
Richter scale
(measures amplitude of waves – gives an absolute measure of an earthquake)

14. Intensity-how much damage an earthquake causes.
Mercalli scale
Not scientific – it is a relative scale but helps people interpret earthquake sizes.

15. The Great Chilean Earthquake
The Earth’s crust is made up of “plates” that float on denser magma below, and move relative to one another. Sometimes two continental plates will crash into one another, and sometimes an oceanic plate will move under a continental one. This is happening off the west coast of South America, which is known as a subduction zone. On 22 May 1960, part of the oceanic plate near the coat of Chile moved under the South American continental plate. This disturbance caused land along the Chilean coast to suddenly drop by about ten feet (three meters), and ground further inland to rise by about twenty feet (six meters).
This abrupt shift caused the biggest earthquake ever recorded, 9.5 and a major tsunami. Many of the buildings in the affected cities had been designed to withstand earthquakes, and a number of smaller quakes in the months leading up to this disaster had given some warning. This lessened the impact of the earthquake itself, but it was the tsunami that was responsible for most of the casualties and damage. The massive wave affected not only Chile, but also caused deaths and damage as far away as Hawaii, Japan, and the Philippines.
Other Big Earthquakes in Modern Times
In terms of events that were studied, measured, and recorded on the Richter scale, the Great Chilean Earthquake was far and away the biggest ever. Keeping in mind that the Richter scale runs along an exponential progression, the next largest was at Prince William Sound, Alaska in 1964, which measured 9.2. The third biggest earthquake ever recorded, was under the Indian Ocean in 2004, clocking in at 9.1 on the Richter scale and generating a formidable tsunami that devastated much of the coastline of Southeast Asia, and killed nearly 228,000 people.
Historical Earthquakes
It is highly probable that some ancient earthquakes were of an even higher magnitude than the 1960 Chile disaster, but because the Richter scale was not developed until the 1930s, it is difficult to quantitatively compare them. Retrospective examination of seismograph records dating back to around 1900 allows estimates to be made, but for earlier events, any assessment of the severity can only be based on eyewitness accounts, and the amount of damage done. For example, the Lisbon earthquake of 1755 was by all accounts very severe, and it generated a massive tsunami which magnified the death toll. The Shaanxi earthquake which occurred in China in the 1500s was the deadliest known to history, killing almost one million people. This event may also have been the biggest known to man, but there is simply no way to tell.

17. This is an isoseismal map showing the impact of the Magnitude 7
This is an isoseismal map showing the impact of the Magnitude 7.7 Alaska Earthquake of July 9, 1958 in Modified Mercalli Scale units. Lituya Bay was in the area of XI intensity. The isoseismal contours near the epicenter parallel the Fairweather Fault. Map information from Seismicity of the United States, (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.

18. Attach picture page to 62