Earthquakes and volcanoes ch 4
Which of the following accurately compares the recurrence interval of magnitude 6 to 7 earthquakes to magnitude 8 earthquakes in the San Francisco Bay area?
Magnitude 8 earthquakes occur about once a century, whereas magnitude 6 to 7 earthquakes tend to occur about once a decade.
What is the projection for earthquakes along the North Antolian fault zone in Turkey?
They will likely follow the pattern that has developed since 1939 and continue to move to the west toward Istanbul.
The tremendous amount of energy involved in thrusting two tectonic plates together results in _____ boundaries having the largest magnitude earthquakes.
convergent
Earth's largest (strongest) earthquakes occur at ______.
convergent boundaries
Which of the following are the projections for earthquakes in the San Francisco Bay region? (Select all that apply.)
There is a 27% chance the Hayward fault will cause a magnitude 6.7 or greater earthquake before 2032. There is a 52 to 72% chance that a 6.7 magnitude earthquake will occur in an urban area before 2032.
Where do most of the subduction-zone earthquakes of today occur?
Around the rim of the Pacific Ocean and in the northeast Indian Ocean
Which of the following natural conditions can increase the destruction caused by earthquakes? (Select all that apply.)
Resonance of seismic waves Soft sediments near the surface
How did tree rings prove useful in determining the timing and occurrence of a large earthquake in the Pacific Northwest in winter of 1700?
They indicated the ground was dropped to a lower elevation, causing an influx of seawater that killed the trees.
Foreshocks can only be labeled as such ______.
after a larger earthquake (mainshock) succeeds them
Most of the fatalities in earthquakes are caused by ______.
buildings and homes collapsing
Rank the type of tectonic plate edge by the magnitude (strength) of the largest earthquakes that occur along it. (Place the boundary that experiences the greatest magnitude earthquakes at the top.)
convergent or push-together transform or slide-past divergent or pull-apart
Tectonic plates collide due to ____ motions, move away from each other due to ____ motions, and slide past one another at transform faults.
convergent, divergent
As a descending slab in a subduction zone is heated from the outside to the inside as it descends, its ability to produce large earthquakes ______ because the rocks' rigidity ______.
decreases; decreases
Match the direction of relative motion to the correct tectonic-plate boundary.
divergent zone --> pull-apart convergence zone --> colliding transform fault --> slide-past
Seismic gaps are formed along segments of an active fault that _______.
have not experienced an earthquake in a long time
_____ but infrequent movements along a locked section of a fault allow it to keep up with a creeping section of the fault.
larger
The next major movement along the Hayward fault is projected to ______.
last about 22 seconds and have about 2 meters of slip along 13 km of fault
The seismic-gap method of forecasting earthquakes involves ______.
looking for segments along a fault that have not moved in a long time as compared to other segments
An earthquake cluster is ______.
the occurrence of a number of earthquakes in the same region over a relatively short amount of time
What caused the large tsunami that struck Indonesia on 26 December 2004?
A long (1,500 km) fault rupture at a convergent plate boundary where a plate is being subducted
What caused the 1989 "World Series" (Loma Prieta) earthquake?
A long rupture within the San Andreas fault zone deep underground that lasted only 7 seconds.
What is a tectonic triple junction?
A point where three plate edges touch
What is the cause of the earthquake hazard in Pacific Northwest of the United States?
A subduction zone
The uplift of the Caucasus and Zagros mountain ranges and earthquakes in their vicinity are being caused by the collision between the ______ and Eurasian tectonic plates.
Arabian
Which of the following describes the spreading center basin related to the northern end of the Gulf of California?
It continues from the Gulf of California in Mexico and finally stops at the end of the Salton Sea in the United States.
What has been the effect of the triple junction located in the northeast Africa since its development about 25 million years ago? (Select all that apply.)
It has created steep escarpments and dramatic valleys in northeast Africa. The influx of seawater into a rift zone has created a sea between Africa and separated the land on the Arabian Plate. It has created the Arabian plate by splitting it from northeast Africa.
Which of the following accurately describes the tectonic setting in the area of the Red Sea, Gulf of Aden, and the northeastern portion of Africa?
Magma beneath northeastern Africa has caused doming, which resulted in gravity-fueled pull-apart faulting and rifting.
What caused the pull-apart basins in the Red Sea fault zone that filled with water to create the Dead Sea and the Sea of Galilee?
Overlaps (steps) in the north--south trending transform (slide-past) fault
Which of the following accurately describes the relationship between buildings and earthquake fatalities?
Poor building design results in a lot of deaths in earthquakes as homes collapse.
What is the tectonic setting of the Dead Sea fault zone?
Pull-apart basins are growing in the overlaps of the Dead Sea transform fault zone.
On the western side of the Arabian plate, what is causing the earthquakes?
Slide-past motion with transform faults
So much stress was released in the 1906 San Francisco earthquake that it took approximately ______ years until large earthquakes occurred there again.
70
How well did the seismic-gap forecasting method work in Chile?
A big earthquake occurred within the identified seismic gap.
Which of the following accurately describes the subparallel fault system that includes the San Andreas fault?
It is a 1,200 km (750 mi) long, right-lateral strike-slip fault system.
Which of the following accurately describe the tectonic boundaries of the Pacific plate?
Slide-past motions dominate in the northeast Pacific and along its eastern border with California. Smaller earthquakes occur at its spreading centers. The Pacific Plate subducts along its northern and western edges.
______ is determined by measuring vertical and horizontal movement along active faults and the length of time needed to accumulate enough stress to trigger a rupture or slip along a fault.
Slip rate
Which of the following accurately characterize spreading center earthquakes?
Small and moderate-size earthquakes dominate. Earthquakes can occur in swarms as magma migrates underground.
Which type of tectonic setting listed below has the largest number of strong earthquakes?
Subduction zones
What is the tectonic setting of Japan?
The Pacific plate is diving under Japan, causing powerful subduction-zone earthquakes there.
Which of the following are transform plate boundary faults? (Select all that apply.)
The San Andreas fault in California The Alpine fault of New Zealand The Enriquillo-Plantain Garden fault in Haiti
Select all the statements below about the San Andreas fault that are accurate.
The fault segment north of Los Angeles is a locked zone and experiences large earthquakes when movement occurs. The section south of San Francisco has frequent small- to moderate-size earthquakes in this "creeping" part of the fault.
Why is there a depth-related distribution in the power of earthquakes at a subduction zone?
The forces that cause earthquakes align differently with depth, and the rock's resistance to stress changes with depth.
What is the reason divergent boundaries have fewer earthquakes than other boundaries?
The rocks located there are warmer, which prevents them from building up a lot of stored stress.
How is the Arabian plate related to the powerful earthquakes occurring in Eurasia?
The spreading centers that formed the Arabian plate are pushing it into Eurasia, causing collision uplifts.
What is creating the down-dropped rift valleys in pull-part basins that have formed the Red Sea, Gulf of Aden, and the Great Rift Valley?
The triple junction of three spreading centers
Foreshocks are defined _____ the mainshock occurs.
after
Earthquakes in the San Francisco Bay region seem to progress to the _____.
north
the ____ _____ for magnitude 6 to 7 earthquakes in the San Francisco Bay region is approximately 10 years, whereas that for magnitude 8 earthquakes is 100 years.
recurrence interval
Short, inactive segments along active faults are called
seismic gaps
True or false: Due to tough building codes, earthquake damage in the San Francisco Bay area is determined only by the strength of the earthquake.
False
Why is Japan subjected to powerful earthquakes?
It is located at a subduction zone.
Which of the following statements accurately characterizes the earthquake activity in the Salton Trough?
It is one of the most earthquake-active areas in the United States.
What does the word slip refer to when used to describe earthquakes?
It means movement has occurred along a fault.
Which of the following accurately describe the earthquake hazards associated with the tectonic collision between India and Asia? (Select all that apply.)
Millions of new buildings are at risk since they were built without seismic-safety inspections. There are large seismic gaps waiting to be filled.
What geologic feature is best associated with continent-continent collision?
Mountain range
Which of the following is true about movements along the entire length of the San Andreas fault?
Movements along the fault occur with different frequencies at different locations.
Most present-day earthquakes occur around the edge of the ____ Ocean.
Pacific
The earthquake forecasting strategy that involves plotting the distribution of earthquakes along a fault to identify the locations at which earthquakes maybe overdue is called the ______ method.
seismic-gap
At transform plate boundaries, tectonic plates on either side ______ each other.
slide past
The enormous movements that occur along a fault when an earthquake occurs are referred to as ______.
slips
Subduction-zone earthquakes are ______.
sometimes extremely powerful
Small earthquakes too weak to knock over buildings or cause fatalities are most likely located at ______.
spreading centers
What is causing the earthquakes in the region of India, China, and Pakistan?
The India plate's push into Asia
How did the Nazca plate move with respect to the South American plate to cause the largest earthquake ever recorded?
The Nazca plate moved eastward and downward beneath the South American plate, causing ruptures along a long and wide stretch of the subduction zone.
What factors contributed to the 1556 earthquake in the Shaanxi Province of China being the deadliest earthquake in history? (Select all that apply.)
The earthquake occurred early in the morning, when people were asleep in their poorly constructed homes. Dwellings were built by digging caves into silt and fine sand that had little cohesion.
Why do the common earthquakes of the Salton Trough tend to occur in swarms?
The earthquakes are related to the forceful movement of magma beneath the crust.
Order the stages involved in forming an ocean basin. (Place the first step at the top.)
centering doming rifting spreading
The double-decker portion of I-880 that collapsed during the 1994 Loma Prieta earthquake did so because it was built on a _____ foundation and had a flawed ____ design.
weak structural
Order the steps involved in the tectonic history of North America with respect to the Pacific Ocean basin. (Put the first step at the top.)
1. the opening and widening of the atlantic pushes north america westward 2. subduction of pacific ocean crust occurs along the west coast. 3. north america collides with spreading centers in the pacific ocean near los angeles 4. a transform fault, the ancestor of the san andreas fault, connects spreading centers to the north and south of los angeles.
Match the stage of ocean basin formation to its description.
centering --> The lithosphere moves over an especially hot region of the mantle. doming --> Mantle heating causes melting, and that results in the surface of the Earth extending upward. rifting --> Gravity pulls an uplifted area apart. spreading --> new seafloor is formed
The locations where ruptures in Earth's crust occur as two sides move past each other in earthquake-generating events are called ______.
faults
Earthquakes are named for the most prominent ____ feature near the epicenter.
geographic
The soft first story of a building created by building a parking garage often results in the first floor ______ when shaken during an earthquake.
pancaking
Why are powerful earthquakes projected to hit Mexico City in the near future?
A large seismic gap exits along a nearby subduction zone.
Earthquakes in the region of Mexico City are caused by ______.
the movements of the Cocos plate as it subducts along a downward thrust fault under the North America plate
At _____ plate boundaries, plates slide past each other horizontally.
transform
The North Anatolian fault has been rupturing in sections with a semiregular pattern to the _____ since 1939; so it is likely that the next big earthquake will occur near Istanbul.
west
What is the Enriquillo-Plantain Garden fault in Haiti?
A left-lateral transform fault (slide-past) related to the boundary between the Caribbean plate and the North American Plate
What factors contributed to the collapse of Interstate 880 during the World Series (Loma Prieta) earthquake? (Select all that apply.)
The supporting columns failed as the soft ground beneath them was deformed by the shaking. The supporting columns failed at joints where the steel bars in them were discontinuous.
Why is an ocean basin opening up north of the Gulf of California in the Salton Sea area of California?
There is a developing spreading-center segment of the rift that opened the Gulf of California.
What is the tectonic setting of Haiti?
Two parallel, east-west trending transform faults pass through Haiti where it sits at the northern edge of the Caribbean plate.
The largest earthquake ever recorded was caused by ______.
a rupture along the Nazca plate as it was converging with the South American plate
When a number of earthquakes occur in a relatively short amount of time, the sequence of events is called a(n) ______.
earthquake cluster
Most earthquakes that occur along fracture zones between segments of midocean ridge occur ______.
on the segments between offset sections of ridge crest
The average slip rate indicates ______.
the average rate of tectonic motion over a given time period
The emergence of the spreading centers in the Red Sea and the Gulf of Aden has caused the formation of the Arabian Plate by cutting it off from ______.
Africa
A large continental collision between Asia and _______ is causing the uplift of the Tibetan Plateau and the continued formation of the Himalayan mountains.
India
The triple junction in ____ has created a rift valley with many topographic features including valleys, domed highlands, lakes, and volcanic peaks.
Africa
In which of these scenarios will the plate subduct? (Select all that apply.)
An older, colder oceanic plate that collides with a younger, warmer oceanic plate A warmer, younger oceanic plate that collides with an older continental plate
Why does liquefaction increase the damage caused by earthquakes?
It causes the sediment supporting buildings to behave like a fluid.
Which of the following is true about the tectonic interaction between India and Asia?
It is a collision zone between two continental plates but was a subduction zone in the past when India's oceanic crust subducted below Asia.
Select the statements below that accurately describe the 1964 earthquake event in Alaska. (Select all that apply.)
It occurred on Good Friday, 27 March. The earthquake had a magnitude of 9.2Mw. The ground shook for a long time, causing many mass-wasting events and a large tsunami.
How did the Arabian tectonic plate form?
It was cut off of the African continent by new spreading centers in the Red Sea and Gulf of Aden.
Which of the following accurately summarizes the earthquake history in the San Francisco Bay region since the 19th century?
Large earthquakes occurred once a decade on average until the 1906 earthquake.
Match the area of the Pacific plate with the dominant type of plate boundary that occurs there.
Southern California and Northern Mexico --> transform or slide-past southeastern pacific ocean --> divergent or pull-apart western and northern pacific ocean --> convergent or push-together
Why are scientists predicting a large earthquake for the Pacific Northwest of the United States?
The Cascadia subduction zone occurs there and appears to be overdue for a large earthquake.
What tectonic action has occurred in western North America over the last 5.5 million years that is responsible for the earthquakes in central and southern California?
The Gulf of California has opened up in a rifting action that has caused land west of the San Andreas fault to attach to the Pacific plate.
The 1964 earthquake in Alaska was very powerful (9.2Mw), yet the loss of human life was not as high as it could have been. What factors helped to limit the loss of life? (Select all that apply.)
The tsunami struck when the tides were low. Above-average temperatures helped to prevent cold-related deaths as heating systems were being repaired. Relatively few people lived in the area at that time of year.
Which side of the Arabian plate has a slide-past motion with its neighboring plate that is causing deadly earthquakes?
The western side
True or false: Some of the earthquakes in the San Francisco Bay area seem to occur in pairs.
true
Most earthquakes along fracture zones occur on the ______ faults between the offset sections of spreading centers.
transform
The San Andreas fault in California is a ___ fault.
transform
Mantle heat that collects at ______ may cause doming and fracturing in a radial pattern. Gravity may then pull the dome apart and allow magma to well up into the three fracture zones.
triple junctions
Which of the following are common sources of data used to conduct tectonic and earthquake research?
Global positioning systems (GPS) Historic written records
Which of the following characterize continental collision zones? (Select all that apply.)
Great earthquakes Thick crust Gigantic seismic zones
What evidence was used to determine a large earthquake occurred in the Pacific Northwest of America in 1700? (Select all that apply.)
Growth rings in trees indicate trees were killed between 1699 and 1700. Historical records from Japan indicate a tsunami occurred at that time.
Which of the following human conditions can increase the destruction caused by earthquakes? (Select all that apply.)
Having a building height that matches the period of the seismic waves so as to produce resonance Building on top of soft sediment Building houses out of mud or brick in earthquake-prone areas
Which of the following contributes to the large number of fatalities caused by earthquakes in Haiti?
Heavy horizontal floor slabs and poorly built concrete buildings are common.
Which of the following accurately summarizes the use of the seismic-gap tectonic forecasting method in Chile?
Historic records, including an event described by Charles Darwin, were used to identify a seismic gap that was then heavily monitored using GPS.
Earthquake pairs seem to occur within ______ in the San Francisco Bay region.
a few years
Where do shallow earthquakes occur in subduction zones? (Select all that apply.)
At the bend in the subduction plate In the overriding plate In the upper portion of the down-going plate
If two tectonic plates converge and no subduction occurs, which of the following is true?
Both of the plates must be continental crust.
How does a locked zone catch up with the movements in a creep zone of the same fault?
By producing larger but less frequent movements
The deadliest earthquake ever recorded occurred in 1556 in _____; most people at the time lived in caves dug into soft sediment that collapsed when it was shaken. (Use just one word for your answer.)
China
Which plate boundary has the lowest earthquake frequency?
Divergent boundaries
What is the cause of the tectonic stress that results in earthquakes in Turkey?
Due to the northward movement of the Arabian plate into Eurasia, Turkey is being rotated and moved westward in what is called escape tectonics.
______ can be used to determine the rate and direction of tectonic motion wherever they are placed along the ground.
Global position systems (GPS)
Which of the following factors contributed to the damage caused by earthquakes in the San Francisco Bay region? (Select all that apply.)
Soft mud and artificial fill used in many areas amplified shaking. Poorly built older buildings made of unreinforced masonry or brick-facade construction
Why does building on filled-in wetlands increase earthquake-related hazards?
Shaking is amplified, and deformation or liquefaction of the ground supporting the buildings can occur.
Which of the following accurately summarizes the earthquake hazard in Turkey?
Strong earthquakes and poorly constructed buildings built on top of soft sediment combine to make earthquakes in Turkey extremely hazardous.
What is the cause of the powerful earthquakes and the resulting large tsunamis that occur in the area of Indonesia?
Subduction of an oceanic plate
Which of the following accurately describe the 1989 "World Series" (Loma Prieta) earthquake? (Select all that apply.)
The movement occurred in a gently left-stepping constraining bend of the San Andreas fault. The vertical fault movement did not offset the ground surface. It was unusually short in duration for an earthquake of its strength.
How are earthquakes named?
The name is taken from the most prominent geographic feature near the epicenter.
Why do subduction zones result in earthquakes with the greatest magnitudes?
The process of subducting a tectonic slab or pushing two continents together requires incredible amounts of energy.
Which of the following has been observed as a pattern in the progression of earthquakes along faults in the San Francisco Bay region?
There seems to be a northward progression of earthquakes along faults.
What is the danger posed by building parking garages on the first floor of buildings?
They are often built with fewer internal walls, lateral supports, and less bracing, which weakens the support for the floors above.
What are the problems posed by the widespread use of concrete floor slabs in Haiti? (Select all that apply.)
They are supported by flimsy concrete columns that fail in earthquakes. They are weak in earthquakes. They are heavy.
Why are the interiors of subducting slabs the only places on the slab where powerful earthquakes can occur at great depth?
They are the only places left on the descending slabs still cold enough to resist the pressures before breaking in a rigid manner.
The San Andreas fault is described as "locked" in the area of San Francisco. What does this mean for the fault?
Virtually all the tectonic stress is stored as elastic strain that will only be reduced in a big earthquake when the fault finally breaks.
A fault is ______.
a place where Earth ruptures and two sides move past each other in earthquake-generating events
