GE 2000 Exam 3 Earthquakes, Volcanoes, Glaciers Exam with 100% Verified Answers
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Module
GE 2000
Institution
GE 2000
GE 2000 Exam 3 Earthquakes,
Volcanoes, Glaciers Exam with 100%
Verified Answers
Why and how do earthquakes occur? - CORRECT ANSWER-Energy that is released
when brittle earth material fails and forms a new fault or slip occurs on an existing fault
Where do earthquakes occur? - COR...
GE 2000 Exam 3 Earthquakes,
Volcanoes, Glaciers Exam with 100%
Verified Answers
Why and how do earthquakes occur? - CORRECT ANSWER-Energy that is released
when brittle earth material fails and forms a new fault or slip occurs on an existing fault
Where do earthquakes occur? - CORRECT ANSWER-Mostly along plate boundaries
(tectonic earthquakes). Other sources are volcanoes, landslides, meteorite impacts,
new hydroelectric projects, nuclear blasts, mining explosions/cave-ins
P wave (primary wave) - CORRECT ANSWER--The fastest velocity, first to arrive (~6.1
km/second)
-Compressional wave
-Elastic deformation of rock is in the direction of wave propagation
s wave (secondary and shear wave) - CORRECT ANSWER--slower than the P-wave
(4.1 km/sec)
-deformation is perpendicular to the direction of wave propagation
-shear can be polarized vertically or horizontally
-can't travel through liquids (requires material to have shear strength)
Surface waves - CORRECT ANSWER--manifestation of P and S waves (body waves)
at the surface
-slowest velocity, but least attenuation with distance
-travel furthest
-large surface waves would have amplitudes of a few cm
-exhibit a lower frequency than body waves
-Two types: Love and Rayleigh
Rayleigh Wave - CORRECT ANSWER-type of seismic wave that travels over the
surface and has an up-and-down motion
Love Wave - CORRECT ANSWER-type of seismic wave that travels over the surface
and has a side-to-side motion
know how a seismograph works - CORRECT ANSWER--During an earthquake, ground-
shaking seismic waves radiate outward from the quake source, called the epicenter
-Different types of seismic waves travel at different speeds and through different parts of
the Earth during a quake.
, know how an earthquake is located - CORRECT ANSWER-Guess a location, depth and
origin time; compare the predicted arrival times of the wave from your guessed location
with the observed times at each station; then move the location a little in the direction
that reduces the difference between the observed and calculated times.
know how to calculate the distance between a seismometer and an epicenter -
CORRECT ANSWER-Measure the difference in arrival times between the first shear (s)
wave and the first compressional (p) wave, which can be interpreted from the
seismogram. Multiply the difference by 8.4 to estimate the distance, in kilometers, from
the seismograph station to the epicenter.
know how seismic waves are used to study the structure of the Earth's interior -
CORRECT ANSWER-As seismic waves pass through the Earth, they are refracted, or
bent, like rays of light bend when they pass though a glass prism.
know numerical relationships between earthquake shaking, earthquake energy, and
magnitude - CORRECT ANSWER-Magnitudes are based on a logarithmic scale (base
10). What this means is that for each whole number you go up on the magnitude scale,
the amplitude of the ground motion recorded by a seismograph goes up ten times.
Using this scale, a magnitude 5 earthquake would result in ten times the level of ground
shaking as a magnitude 4 earthquake (and about 32 times as much energy would be
released).
know what the Mercalli Index represents - CORRECT ANSWER-A Measure of Intensity
(destructiveness); descriptive scale
know what the Richter magnitude represents and the numerical relationship between
magnitudes - CORRECT ANSWER-- Based on the amplitude of the largest P or S wave
- Correction for distance
- Representative of the intensity of ground shaking
Shortcomings of the Richter Scale - CORRECT ANSWER--Instrument specific
-Based on California geology
-Doesn't account for duration
-Underestimated the size of large earthquakes
know what the moment magnitude scale is based on, what it measures, and the
numerical relationship between different magnitudes - CORRECT ANSWER--
representative of energy release
-Seismic moment = rock strength x surface area of rupture x amount of rock
displacement
-Each increase in magnitude = ~ 30x increase in energy release!
know how seismic waves behave in the earth - how and why velocity, direction and
wave amplitude changes - CORRECT ANSWER--Seismic energy propagates as elastic
waves, and therefore depends on the elastic properties of the rock:
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