Natural Disasters Exam 2-Chapter 5 Earthquakes

The crustal thickness in the Great Basin is ______ than mid-continental North American Crust

Thicker than oceanic crust and thinner

T/F Aftershocks of the 1811-12 New Madrid, Missouri, earthquakes are still occurring today

True

T/F Human activity has likely triggered earthqukes with magnitudes between 3 and 5

True

T/F Nevada has several gaps in the belt of historic seismicity, suggesting residents in these seisnuc gaps may be

True

T/F Ocean ridge spreading still occurs offshore of northernmost California, Oregon, Washington, and southern British Columbia, as well as in the Gulf of California

True

T/F Pumping fluids into Earth has been found to sometimes trigger small earthquakes (magnitudes <5)

True

At Hebgen Lake in 1959 an earthquake larger than magnitude 7 greatly affected _____

Yellowstone National Park

The New Madrid earthquakes are apparently related to an old buried ___________.

rift zone

T/F Earthquakes epicenters east of the Rocky Mountains are in random locations and do not cluster in certain areas

False

T/F The Imperial valley sits on an actively closing ocean floor

False

T/F The duration of shaking in 1985 in Mexico City was decreased due to seismic energy being trapped within the soft sediments

False

T/F Thrust faults that do not reach the surface are called dark thrusts

False

The dominant type of faulting in the Great Basin region is

Normal Faulting

When rock heats and liquefies into magma its volume _______.

A. expands, and neighboring brittle rock must fracture and move out of the way.

When compared to California, seismic energy in the eastern U.S. is transmitted __________________________.

A. more effectively in the older, more solid rocks

Paleoseismologic analysis of trenches cut across faults and folds in the New Madrid, Missouri, area has led the U. S. Geological Survey to forecast a 25% chance of magnitude ___________.

B. 6 to 7

When magma is on the move at shallow depths it commonly generates a swarm of _______.

D. Large earthquakes referred to as harmonic tremors

Earthquakes in Hawaii are mostly related to __________.

D. Movement of volcanic magma beneath the ground

The Charleston, South Carolina, earthquake of 1886 occurred along a seismic belt that may be related to _______________.

c. An adjacent oceanic fracture zone on the Atlantic seafloor