Geography 300 - Earthquakes Flashcards

Seismic Waves
Terms Definitions
Earthquake
Sharp release of energy that sends seismic waves traveling through Earth's crust at the moment of rupture, outward from a fault or in association with volcanic activity
February 1975
Frist earthquake was predicted. 90% of buildings fell in city of Haicheng. Thousands of lives were claimed
Tangshan Earthquake
Official death toll was $250,000. No forecast or warning. 7.4 magnitude. 95% of buildings destroyed and 80% industrial structures destroyed
Focus/Hypocenter
Subsurface area along a fault plane where the motion of seismic waves is initiated
Epicenter
The area at the surface directly above the focus
Shockwaves
Shockwaves radiate outward through the rust from the focus and the epicenter. Seismic waves are conducted throughout the planet to distant instruments. Scientist explore earth's interior using the seismic wave patterns and nature of their transmission through the layers of the planet.
Aftershock
Occurs after the main shock. It shares the same general area of the epicenter. Some rival the main tremor in magntude
Foreshock
Comes before the main shock. Pattern of a foreshock is regarded as important consideration in the forecasting effort.
Tectonic Earthquake
Associated with faulting
Seismographs
Instrument for recording seismic events. It records vibrations transmitted as waves of energy throughout Earth's interior and in the crust.
How do scientist rate earthquakes?
Two scales - Qualitative damage intensity scale and quantitative magnitude of energy released scale.
Shockwaves
Shockwaves produced by an earthquake radiate outward through the crust from the focus and epicenter. Some are conduced throughout the plant to distant instruments.
1992 Landers Quake
Earthquake in southern California. Two dozen foreshocks occurred
Mercalli scale
A damage intensity scale. Measures damage after earthquake to terrain, structures. Its in Roman numbers from I to XII. It was designed in 1902 and revised in 1931
1960 Chile Quake
Strongest earthquake with a Richter scale of 9.6 and Mercalli of XII. Fault broke extended over 629 miles
Richter Scale
measures quantitative magnitude of energy. Developed by Charles Richter in 1935. Each whole number represents a 31.5 fold increase in energy released
Moment Magnitude Scale
Revised the Richter Scale. Its been in use sice 1993. Used to more accurately measure large earthquakes. Considers the amount of fault slippage, size of the surface or subsurface and nature of materials that faulted. Rated Northrdique quake as 6.8. It considered the upward ground movement that Richter underestimated
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