1. Earthquakes
Basic Introduction

3. Seismometer

4. Seismogram

5. P waves

6. S Waves FIGURE 10.10 Different types of earthquake waves.
(b) Shear waves can be produced by moving the end of a rope up and down. S-waves are shear body waves. As the waves pass through rock, the vibration direction is perpendicular to the direction of the wave movement.
Earth: Portrait of a Planet, 4th Edition
Copyright © 2012 W. W. Norton & Company

7. FIGURE 10.14 The method for locating an earthquake epicenter.
(a) Seismic waves travel at different velocities. The greater the distance between the epicenter and the seismograph station, the longer it takes for earthquake waves to arrive, and the greater the delay between the P-wave and S-wave arrival times.
Earth: Portrait of a Planet, 4th Edition
Copyright © 2012 W. W. Norton & Company

8. LOCATING THE EPICENTER OF AN EARTHQUAKE
Three seismograms are needed (Triangulation) Costa Rica, Ireland and Philippines

9. Seismogram for Costa Rica
Surface wave
S wave
P wave
10:15AM
10:20AM
10:25AM
10:30AM
Seismogram for Costa Rica

11. Richter Scale Amount of energy released during an earthquake

12. Destructiveness (Extent of damage)
MERCALLI INTENSITY SCALE
Intensity
Description
Destructiveness (Extent of damage) I
Instrumental
Detected only by instruments; causes no damage II
Feeble
Felt by a few stationary people, especially in the upper floors of buildings; suspended objects like lamps may swing.
III
Slight
Felt indoors; standing automobiles sway on their suspensions; it seems as though a heavy truck is passing. IV
Moderate
Shaking awakens some sleepers; dishes and windows rattle. V
Rather strong
Most people awaken; some dishes and windows break, unstable objects tip over; trees and poles sway. VI
Strong
Shaking frightens some people; plaster walls crack, heavy furniture moves slightly, and a few chimneys crack but overall little damage occurs.
VII
Very Strong
General alarm; Most people are frightened and run outside; a lot of plaster cracks, windows break, some chimneys topple, and unstable furniture overturns; poorly constructed buildings sustain considerable damage.
VIII
Destructive
Many chimneys and factory smokestacks topple; masonry cracks; heavy furniture overturns; substantial buildings sustain some damage, and poorly constructed buildings sustain severe damage. IX
Ruinous
Some buildings collapse; frame buildings separate from their foundations; most buildings sustain damage, and the ground cracks, underground pipes break and rails bend: some landslides occur. X
Disastrous
The ground severely cracks in places; most masonry structures and some well constructed wooden structures are destroyed; many landslides occur along steep slopes; some bridges collapse; some sediment liquefies; concrete dams may crack; facades on many buildings collapse; railways and roads suffer severe damage. XI
Very Disastrous
Few masonry buildings remain standing; many bridges collapse; broad fissures form in the ground; most pipelines break; severe liquefaction of sediment occurs; some dams collapse; facades on most buildings collapse or are severely damaged.
XII
Catastrophic
Earthquake waves cause visible undulations of the ground surface; objects are thrown up off the ground; there is complete destruction of buildings and bridges of all types.