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Which four states account for 91% of all U.S.earthquakes of magnitude 3.5 and above?


A) California,Alaska,Washington,Oregon
B) California,Alaska,Washington,Hawaii
C) California,Alaska,Hawaii,Nevada
D) California,Hawaii,Washington,Nevada
E) California,Hawaii,Nevada,Idaho

F) A) and B)
G) B) and D)

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The Owens Valley quake of 1872 is estimated to have had a magnitude of 7.8 to 8,indicating that big earthquakes can and do happen far away from the coastal zone and the San Andreas fault.

A) True
B) False

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Adjustments related to plate-tectonic activity cause earthquakes from Washington to New Mexico,from Montana to California,and at other points throughout the West.

A) True
B) False

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Prehistoric earthquakes may be interpreted using faulted pond sediments.The amount of offset of sediment layers from one earthquake is proportional to the ________________.


A) amount of time since the last major earthquake
B) amount of radioactive material in the sediment
C) earthquake magnitude
D) isostatic anomaly

E) A) and C)
F) A) and B)

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When rock heats and liquefies into a magma its volume _____________.


A) expands,and neighboring brittle rock must fracture and move out of the way
B) decreases and neighboring brittle rock collapses to make up for the loss of volume
C) does not change
D) decreases due to sublimation

E) A) and B)
F) A) and C)

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The Great Basin region between the eastern Sierra Nevada in California and the Wasatch Mountains in Utah ______________________ in response to plate tectonic forces.


A) has been compressed in an east-west direction
B) has expanded in an east-west direction
C) has been compressed in a north-south direction
D) has expanded in a north-south direction
E) is now a subduction zone

F) A) and D)
G) C) and E)

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In the Pacific Northwest,stresses are transmitted upward from the subducting plates,forming strike-slip faults that rupture the surface,as in Seattle.

A) True
B) False

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The epicenters of the larger New Madrid,Missouri,earthquakes line up along the Mississippi River Valley,possibly because of an ancient rift valley,known as the Reelfoot rift,formed about 550 million years ago.

A) True
B) False

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Today,North America has several small- to medium-sized plates subducting beneath its ____________.


A) eastern margin
B) western margin
C) northern margin
D) southeastern margin
E) margins,all around the North American plate

F) None of the above
G) A) and E)

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Human activity has induced powerful earthquakes (magnitudes > 6).

A) True
B) False

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Which of the following states has the highest earthquake risk?


A) Michigan
B) Nebraska
C) Arkansas
D) North Dakota
E) Florida

F) C) and E)
G) D) and E)

Correct Answer

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In the central United States,ancient rift valleys remain from failed spreading centers and these ancient rifts today are zones of weakness whose faults can be reactivated due to long-distance effects of Atlantic plate spreading and Pacific plate collision.

A) True
B) False

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Nevada has several gaps in the belt of historic seismicity,suggesting residents in these seismic gaps may be in for some future earthquakes.

A) True
B) False

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The San Andreas fault's earthquakes in historic time include which of the following?


A) a magnitude 8+ caused by a 225-mi-long rupture in central California in 1857
B) a magnitude 8+ due to a 265-mi-long rupture passing through the San Francisco Bay region in 1906
C) a magnitude 7.1 unleashed by a 25-mi-long rupture near Santa Cruz in 1989
D) All of these are correct.

E) A) and D)
F) A) and C)

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Earthquake epicenters east of the Rocky Mountains are in random locations and do not cluster in certain areas.

A) True
B) False

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The dominant type of faulting in the Great Basin region is ______________.


A) normal faulting
B) reverse faulting
C) strike slip faulting
D) thrust faulting
E) transform faulting

F) A) and E)
G) A) and B)

Correct Answer

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We know that the part of California on the Pacific plate will not break off in a giant earthquake and sink into the Pacific Ocean because ______________________.


A) the Pacific plate is being subducted beneath California instead
B) the San Andreas fault is a thrust fault,not a normal fault
C) of isostasy
D) convective forces
E) oceanic circulation

F) C) and D)
G) A) and E)

Correct Answer

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How does a locked zone of a large strike-slip fault catch up with a creep zone?


A) by frequent earthquakes around magnitude 4
B) by infrequent and large creep events
C) by frequent and large creep events
D) by frequent but small earthquakes
E) by infrequent but large fault movements (i.e. ,large quakes)

F) C) and E)
G) A) and B)

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The southernmost segment of the San Andreas fault,from San Bernardino to the Salton Sea,is a complex zone that has generated several truly large earthquakes in historic times,but it has no locked zones within it.

A) True
B) False

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The ________ segment of the San Andreas fault is the only one not to have a long rupture in historic time.In prehistory,it has ruptured every 250 years on average,but the last big movement was in 1680.


A) Coachella Valley
B) Loma Prieta
C) Cholame to San Bernardino
D) Landers

E) A) and C)
F) C) and D)

Correct Answer

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