2. Fig
W. W. Norton

3. Fig ab
W. W. Norton

4. W. W. Norton

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

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

9. Richter Scale Amount of energy released during an earthquake

10. 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.