EarthquakesBasic Introduction
Seismometer
Seismogram
P waves
Earth: Portrait of a Planet, 4th EditionCopyright © 2012 W. W. Norton & Company
S Waves
Earth: Portrait of a Planet, 4th EditionCopyright © 2012 W. W. Norton & Company
LOCATING THE EPICENTER OF AN EARTHQUAKE
Three seismograms are needed (Triangulation)
Costa Rica, Ireland and Philippines
Seismogram for Costa RicaP wave
S wave
Surface wave
10:15AM 10:20AM 10:25AM 10:30AM
Seismogram for Costa Rica
Richter Scale
Amount of energy released during an earthquake
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.
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