Chapter 5 Earthquakes Throughout the United States and Canada
Extensional forces occurring in the ____ region have resulted in north-south oriented, back-tilted mountain ranges that have made the area susceptible to many earthquakes.
Great Basin
The combined movements of the ____, ____, and ____ plates account for most of the seismic activity experienced in North America.
Pacific; North American; Farallon
The ____ rift is ancient, having formed about 550 million years ago.
Reelfoot
What is the name given to the rift found underlying the basement rocks in the New Madrid region?
Reelfoot
One prominent example of a filed rift in the united States is the ____.
Reelfoot rift
Which of the following statements accurately describes the movement of a normal fault?
Tensional forces pull one rock mass away and down from another.
The largest earthquake to occur outside of California and Alaska took place in two different states: ____ and ____.
Washington; Hawaii.
Which two effects on ground surface do dams have that can trigger earthquakes?
Water seeping underneath the impounded reservoir creates a region of high pressure that may cause fault movement; Dams cause the earth beneath them to sink isostatically, increasing pressure.
The 1975 Hawaiian earthquake demonstrated that ____.
earthquakes can sometimes generate volcanic activity
Our understanding of how ____ movements work is continually being advanced through field equipment and instrumentation improvements.
fault
The Landers earthquake demonstrated that, on rare occasions, ____.
fault movements can occur across multiple faults
While there is no question that the process nicknamed ____ has increased fossil-fuel energy production in the United States, many environmental concerns remain, not to mention its potential for causing earthquakes.
fracking
According to elastic-rebound theory, rocks do not constantly move in response to stress because their rough and irregular surfaces generate ____ that retards movement.
friction
The extension and faulting of the Rio Grande rift is due to ____.
heating from below the crust
Better understanding of fault movements largely comes from ____.
improvements to field equipment and instrumentation
In 1984, a group of scientists using an army of instruents predicted an earthquake for the Parkfield, California, area would take place by 1993. An earthquake actually occurred ____.
in 2004, 16 years late
The Brigham City segment of the Wasatch Front fault system is prime candidate fr a major potential earthquake because ____.
it has not moved in the past 2,400 year
Found on the island of Kilauea, earthquakes can sometimes be triggered by the subsurface movement of ____ that creates normal-fault, down-dropped valleys.
magma
Harmonic tremors are generated when ____.
magma moves at shallow depths
With regards to earthquakes and seismology, Iben Browning is best known for ____.
making unfounded predictions of a major earthquake in the middle United States in the 1990s.
Scientists utilize the sedimentary rock record to estimate the magnitude of ancient earthquakes by ____.
measuring the amount of offset between layers of sedimentary rock
Three of the most significant earthquakes to hit the Puget Sound area originated ____.
near the subducting Juan de Fuca plate
The 1949, 1965, and 2001 Puget Sound earthquakes were the result of ____ fault movement within the Juan de Fuca plate.
normal
Southern California experiences many earthquakes because ____.
northward movement along the San Andreas fault creates many thrust faults
The majority of earthquake hazards in the United States are connected to ____.
ongoing subduction along the west coast of North America
The large felt area of the 1886 Charleston earthquake is the result of the ____.
persistence of long-period seismic waves moving through solid bedrock
The Great Basin region is subject to many earthquakes because of ____.
regional extension in the Basin and Range province
Isostatic rebound occurring near the Reelfoot rift has been suggested as a possible trigger for earthquakes. The isostatic rebound is the result of ____.
removal of sediments following the retreat of glaciers
The city of Seattle is very susceptible to earthquake-related damage because it ____.
sits atop a deep basin filled with soft sediments.
The 1983 Borch Peak earhquake in Idaho had an unusual effet on Thousand Springs Valley when the earthquake ____.
squeezed water from the subterranean aquifers, creating fountains of water 3 to 6 m high
Underground pumping of liquids can trigger earthquakes, first by adding ____ and then by reducing ___ along faults.
stress; friction
An earthquake ____ occurs as a series of earthquakes in succession without a mainshock.
swarm
Two earthquakes struck the Big Island of Hawaii in 2006. The first was the result of ____, and the second was caused by ____.
tensional forces; compressional forces
Numerous major human settlements, such as Albuquerque, New Mexico, El Paso, Texas; and Ciudad Juarez, Mexico, are located right along the Rio Grande rift. Human settled here because ____.
the Rio Grande river follows the rift
Rank the following states in order of earthquake occurrence, placing the state with the greatest frequency of earthquakes at the top and the state with the lowest frequency of earthquakes at the bottom.
1. Alaska 2. California 3. Hawaii 4. Idaho 5. Utah
The amount of measured deformation in southern California means that a magnitude 7 earthquake could occur as often as every ____ years.
10
The ____ earthquake produced no surface faulting, suggesting fault movement occurred below 20 km in depth.
1886 Charleston
The 1872 Owens Valley earthquake had an estimated magnitude of ____.
7.4
Based upon current fault movements, California will ultimately collide witht the state of ____, switching from sunny beaches to ski slopes.
Alaska
____ has been proposed as the trigger mechanism for earthquakes along the Reelfoot rift.
Isostatic rebound
Western US
Layers of soft sediment susceptible to violent shaking; Updated building codes designed to withstand earthquakes; Lower population densities
The petroleum industry has known for some time hat human activity can produce earthquakes, particularly whe ____.
Liquids are pumped underground at high pressures.
____ is the most common earthquake hazard that people encounter.
Objects falling on one's head
Eastern US
Older buildings unable to withstand earthquake shaking; Underlain by older, solid rocks that effectively transmit earthquake energy; Large population densities
In 1872, the ____ fault zone broke loose, creating a large earthquake that was felt and recorded by John Nuir at his cabin in Yosemite Valley.
Owens Valley
Several lines of evidence point to a major earthquake occurring near the city of ____ 1,100 years ago, including numerous landslides and tsunami deposits dated to this time period.
Seattle
A number of large cities lie within the New Madrid seismic zone, including ____.
St. Louis; Memphis; Nashville;
What lines of evidence support the hypothesis that a large earthquake struck Seattle about 1,100 years ago?
The shoreline along Restoration point shows significant uplift; Coarse sediment layers at the bottom of Lake Washington appear to have earthquake; Six major rock avalanches in the Olympic Mountains are dated to this period.
A scarp is ____.
a steep slope created by the movement of faults
The tectonic activity in Charlevoix, Quebec, is the result of ____.
an ancient meteorite impact that created faults in the underlying bedrock
The radiocarbon clock starts "ticking" when ____.
an organism dies
Big earthquakes do not happen every year in the United States, but their cumulative financial effects are forecast using ____.
annualized earthquake losses
In eastern North America, large earthquakes ____.
are associated with low-strain regions; mostly occur at the sites of failed rifts; lack significant recent faulting
Underground fluid pumping sometimes triggers earthquakes because the fluids ____.
are forced into ancients fault, causing them to reactivated
In the United States, 4.4 ____ dollars in annualized earthquake losses are projected.
billion
An 18-hour volcanic eruption was started by the 1975 earthquake in Hawaii. The earthquake triggered the eruption by ____.
causing gases to escape from subsurface magma
In terms of characteristics, earthquakes of Eastern North America most closely resemble those that occur in ____.
central North America
The damage cause by the 2001 Tacoma-Olympia earthquake was largely the result of ____.
the setting of soft sediments from shaking; inadequate earthquake protections built into older structures.
Following the 1965 Puget SOund earthquake, new building codes were enacted to protect against earthquake damage. These changes included ____.
tying homes to their foundations more securely; strengthening highway bridges; removing water storage tanks from the tops of buildings.
