Ch 4 reading assignment

Match the stage of ocean basin formation to its description. Centering Doming Rifting Spreading 1. new seafloor is formed 2. mantle heating causes melting, and that results in the surface of the earth extending upward 3. the lithosphere moves over an especially hot region of the mantle 4. gravity pulls an uplifted area apart

3 2 4 1

So much stress was released in the 1906 San Francisco earthquake that it took approximately ______ years until large earthquakes occurred there again. 70 125 35

70

______ 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. Subduction angle Seismic gap Slip rate

Slip rate

Where do shallow earthquakes occur in subduction zones? ___ In the overriding plate ___ In the upper portion of the down-going plate ___ At the bend in the subduction plate ___ Along the bottom of the down-going plate

In the overriding plate In the upper portion of the down-going plate At the bend in the subduction plate

The soft first story of a building created by building a parking garage often results in the first floor ____ when shaken during an earthquake.

collapsing

Seismic gaps are formed along segments of an active fault that _______. ___ experience frequent earthquakes ___ have not experienced an earthquake in a long time ___ have never experienced earthquakes

have not experienced an earthquake in a long time

What is the Enriquillo-Plantain Garden fault in Haiti? A thrust-fault related to the eastern portion of Haiti being pushed up and over the eastern portion by seafloor spreading A left-lateral transform fault (slide-past) related to the boundary between the Caribbean plate and the North American Plate A radial fracture pattern that is forming in relation to volcanic activity on the island A fracture related to the post-glacial rebound happening in response to the last Ice Age

A left-lateral transform fault (slide-past) related to the boundary between the Caribbean plate and the North American Plate

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. African Arabian Indo-Australian

Arabian

A large continental collision between Asia and ____ is causing the uplift of the Tibetan Plateau and the continued formation of the Himalayan mountains.

India

Why does liquefaction increase the damage caused by earthquakes? It causes the sediment supporting buildings to behave like a fluid. It changes the period of the buildings above to match that of the earthquake. It causes ground tsunami to form that can travel for long distances while knocking over buildings along the way. It increases the rigidity of the underlying ground.

It causes the sediment supporting buildings to behave like a fluid.

Earthquake pairs seem to occur within ______ in the San Francisco Bay region. a couple of minutes a few days a few years

a few years

A fault is ______. ___ a type of earthquake in which seismic waves, or evidence of their passing, are visible at Earth's surface ___ an area of weakness in a rock formation that may break due to tectonic pressures ___ the zone between rock masses where a gap exists ___ a place where Earth ruptures and two sides move past each other in earthquake-generating events

a place where Earth ruptures and two sides move past each other in earthquake-generating events

Most of the fatalities in earthquakes are caused by ______. buildings and homes collapsing people falling into chasms brain injuries suffered while being shaken by the ground heart attacks related to the sudden shock of the event

buildings and homes collapsing

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 ___ identifying regions along the fault in which seismic waves do not pass when earthquakes occur ___ searching for areas along a fault in which the dominate rock type switches to another, less-resistant type of rock ___ finding the locations along a fault in which large spaces are slowly opening up between two sides

looking for segments along a fault that have not moved in a long time as compared to other segments

Earthquakes in the San Francisco Bay region seem to progress to the ____.

north

1. convergent zone 2. divergent zone 3. transform fault ___ colliding ___ slide-past ___ pull-apart

1 3 2

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.) 1. convergent or push-together 2. divergent or pull-apart 3. transform or slide-past

1 3 2

Match the area of the Pacific plate with the dominant type of plate boundary that occurs there. ___ Southern California and Northern Mexico ___ Southeastern Pacific Ocean ___ Western and Northern Pacific Ocean 1. divergent or pull-apart 2. convergent or push-together 3. transform or slide-past

3 1 2

What factors contributed to the collapse of Interstate 880 during the World Series (Loma Prieta) earthquake? The supporting columns failed at joints where the steel bars in them were discontinuous. The supporting columns failed as the soft ground beneath them was deformed by the shaking. Bricks used to build the supporting columns fractured in the shaking produced by the earthquake. Sections built on sand and gravel rolled back and forth farther than projected, causing them to fail.

The supporting columns failed at joints where the steel bars in them were discontinuous. The supporting columns failed as the soft ground beneath them was deformed by the shaking.

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 ___ A series of transform faults that connects the Mediterranean Sea and the Indian Ocean ___ A continental collision between northern Africa and southern Europe ___ A snaking spreading center that is offset by many transform faults

The triple junction of three spreading centers

Most earthquakes along fracture zones occur on the ______ faults between the offset sections of spreading centers. transform reverse normal

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. quarries active faults triple junctions subduction zones

triple junctions

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 stages involved in forming an ocean basin. (Place the first step at the top.) Doming Rifting Centering Spreading

Centering Doming Rifting Spreading

Earthquakes are named for the most prominent ____ feature near the epicenter.

geographic

If two tectonic plates converge and no subduction occurs, which of the following is true? Both of the plates must be continental crust. Both of the plates must be oceanic crust. One plate is composed of oceanic crust, and one plate is composed of continental crust.

Both of the plates must be continental crust

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 every 25 years, whereas magnitude 6 to 7 earthquakes tend to occur about twice a century. All magnitudes greater than 6 tend to have the same recurrence interval of 17 years. Magnitude 6 to 7 earthquakes tend to occur once a century, whereas magnitude 8 earthquakes occur about once a decade. Magnitude 8 earthquakes occur about once a century, whereas magnitude 6 to 7 earthquakes tend to occur about once a decade.

Magnitude 8 earthquakes occur about once a century, whereas magnitude 6 to 7 earthquakes tend to occur about once a decade.

On the western side of the Arabian plate, what is causing the earthquakes? A triple collision between the Eurasian, African, and Arabian plates A subduction zone Slide-past motion with transform faults A spreading center

Slide-past motion with transform faults

Which of the following accurately characterize spreading center earthquakes? ___ Small and moderate-size earthquakes dominate. ___ The earthquakes tend to produce S waves but not P waves. ___ Large earthquakes occur as the rate of spreading increases. ___ Earthquakes can occur in swarms as magma migrates underground.

Small and moderate-size earthquakes dominate. Earthquakes can occur in swarms as magma migrates underground.

Select all the statements below about the San Andreas fault that are accurate. The section south of San Francisco has frequent small- to moderate-size earthquakes in this "creeping" part of the fault. The southern-most segment of the San Andreas fault has caused some of the largest earthquakes ever recorded in California. The section in San Francisco has large earthquakes that occur about every two years in this "jumping" part of the fault. 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. The fault segment north of Los Angeles is a locked zone and experiences large earthquakes when movement occurs.

Which of the following accurately describe the 1989 "World Series" (Loma Prieta) earthquake? (Select all that apply.) The vertical fault movement did not offset the ground surface. It was unusually short in duration for an earthquake of its strength. The epicenter was in the northern most section of the San Francisco Bay. 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. The movement occurred in a gently left-stepping constraining bend of the San Andreas fault.

Which side of the Arabian plate has a slide-past motion with its neighboring plate that is causing deadly earthquakes? The eastern side The western side The southern side The northern side

The western side

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 be relatively a nonevent due to the enforcement of stronger building codes and better earthquake preparedness cause trillions of dollars of damage and push the land to the west of the fault into the Pacific Ocean cause just under 50 million dollars of damage and possibly a few dozen deaths

last about 22 seconds and have about 2 meters of slip along 13 km of fault

The average slip rate indicates ______. how long it will be until the next major earthquake occurs along the fault how much movement occurs along a fault in a given year the amount of frictional resistance between two tectonic plates the average rate of tectonic motion over a given time period

the average rate of tectonic motion over a given time period

At ____ plate boundaries, plates slide past each other horizontally. (Enter only one word per blank.)

transform

Order the steps involved in the tectonic history of North America with respect to the Pacific Ocean basin. (1-4) ___ the opening and widening of the atlantic pushes north america westward ___ subduction of pacific ocean crust occurs along the west coast ___ a transform fault, the ancestor of the san andreas fault, connects spreading centers to the north and south of los angeles ___ north america collides with spreading center in the pacific ocean near los angeles

1 2 4 3

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. A short rupture in the San Andreas fault directly beneath Candlestick Park that lasted almost 2 minutes. A horizontal movement at the southern portion of the San Andreas fault that moved areas west of the fault 2 meters farther to the west.

A long rupture within the San Andreas fault zone deep underground that lasted only 7 seconds.

What is a tectonic triple junction? A plate boundary that produces normal, reverse, and thrust faulting A point where three plate edges touch A tectonic plate that has all three types of boundaries along at least one of its sides A fault that is divided into three segments

A point where three plate edges touch

In which of these scenarios will the plate subduct? A warmer, younger oceanic plate that collides with an older continental plate A larger continental plate that collides with a smaller continental plate 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 An older, colder oceanic plate that collides with a younger, warmer oceanic plate

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 ______. the Indian Ocean's crust Asia Africa Europe

Africa

The triple junction in ____ has created a rift valley with many topographic features including valleys, domed highlands, lakes, and volcanic peaks.

Africa

Where do most of the subduction-zone earthquakes of today occur? ___ In the southern Indian Ocean and around the continent of Antarctica ___ Along the west coast of Africa and the southern shores of the Arctic Ocean ___ Around the rim of the Atlantic Ocean and in the eastern Mediterranean Ocean ___ Around the rim of the Pacific Ocean and in the northeast Indian Ocean

Around the rim of the Pacific Ocean and in the northeast Indian Ocean

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 By transitioning to a creep zone after a large fault does occur By taking a more direct path than a creep zone does By slow but steady motion along the 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.

China

Which plate boundary has the lowest earthquake frequency? Divergent boundaries Convergent boundaries Transform faults

Divergent boundaries

What factors contributed to the 1556 earthquake in the Shaanxi Province of China being the deadliest earthquake in history? There was a high tide when the earthquake struck. Dwellings were built by digging caves into silt and fine sand that had little cohesion. Heavy snow in the days before the event allowed large avalanches to form. 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. The earthquake occurred early in the morning, when people were asleep in their poorly constructed homes.

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

Which of the following characterize continental collision zones? Thin crust Gigantic seismic zones Great earthquakes Thick crust Deep earthquakes

Gigantic seismic zones Great earthquakes Thick crust

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. The earthquakes are among the most powerful in the world. The offshore topography is ideal for tsunami formation. the French colonials required that buildings be made out of wood.

Heavy horizontal floor slabs and poorly built concrete buildings are common.

What has been the effect of the triple junction located in the northeast Africa since its development about 25 million years ago? ___ It has created steep escarpments and dramatic valleys in northeast Africa. ___ It has created the Arabian plate by splitting it from northeast Africa. ___ It has caused powerful subduction zone earthquakes that have killed hundreds of thousands of people in the region. ___ 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 steep escarpments and dramatic valleys in northeast Africa. It has created the Arabian plate by splitting it from northeast Africa. The influx of seawater into a rift zone has created a sea between Africa and separated the land on the Arabian Plate

Which of the following accurately describes the subparallel fault system that includes the San Andreas fault? It is a 4,880 km (3,032 mi) long, high-angle reverse fault system. It is a 3,250 km3 (2,020 mi3) wide radial normal fault system. It is a 500 km (310 mi) long, low-angle thrust fault system. It is a 1,200 km (750 mi) long, right-lateral strike-slip fault system.

It is a 1,200 km (750 mi) long, right-lateral strike-slip fault system.

Which of the following is true about the tectonic interaction between India and Asia? ___ It is an oceanic collision zone between two young plates, which is resulting in mountain building rather than subduction. ___ India and Asia are sliding past one another in a horizontal motion. ___ 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. ___ India is pulling away from Asia by moving to the southeast, and the motion is forming a rift zone in front of the mountains.

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.

How did the Arabian tectonic plate form? It broke off of the southern portion of the Eurasian plate in a rebound effect as India collided with Asia. It was cut off of the African continent by new spreading centers in the Red Sea and Gulf of Aden. It broke off of India and was pushed to the northwest by a spreading center. It formed from a hot spot that stayed in one place long enough to create a tectonic plate.

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 in the region have occurred at least once every 8 to 12 years since the early 19th century. Large earthquakes occurred once a decade on average until the 1906 earthquake. After the 1906 earthquake, large earthquakes became more frequent. There have been no discernible patterns in the history of large earthquakes in the San Francisco Bay region.

Large earthquakes occurred once a decade on average until the 1906 earthquake.

_____ but infrequent movements along a locked section of a fault allow it to keep up with a creeping section of the fault. Larger Faster Smaller Slower

Larger

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. ___ A subduction zone in the Red Sea and one in the Gulf of Aden are resulting in large earthquakes that are ripping the surface of the land apart. ___ The collision of Africa with the Middle East is creating downward folds in some areas and upward, mountain-forming zones in others.

Magma beneath northeastern Africa has caused doming, which resulted in gravity-fueled pull-apart faulting and rifting.

Which of the following accurately describe the earthquake hazards associated with the tectonic collision between India and Asia? ___ Millions of new buildings are at risk since they were built without seismic-safety inspections. ___ Recently earthquakes have been hitting mega-cities in the region. ___ There are large seismic gaps waiting to be filled. ___ Powerful earthquakes are unlikely to occur in the region.

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? Oceanic trench Volcanic arc Rift valley Mountain range

Mountain range

Which of the following is true about movements along the entire length of the San Andreas fault? The entire fault seems to move in the same fashion along its length. The frequency and location of earthquakes along the length of the San Andreas fault seem to be random. Movements along the fault occur with different frequencies at different locations.

Movements along the fault occur with different frequencies at different locations.

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? ___ A collision between the Arabian plate and the Eurasia plate ___ The formation of a new subduction zone in the eastern Mediterranean ___ Overlaps (steps) in the north--south trending transform (slide-past) fault ___ The development of a new spreading center on land

Overlaps (steps) in the north--south trending transform (slide-past) fault

Which of the following accurately describes the relationship between buildings and earthquake fatalities? Houses designed out of inorganic natural materials such as rock and mud make ideal shelters in earthquakes. Poor building design results in a lot of deaths in earthquakes as homes collapse. Buildings rarely kill people in earthquakes. There is little variation in how much building design impacts the number of fatalities an earthquake causes.

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. It is a subduction zone where the Mediterranean Sea is being forced under the Eurasian plate. It is an extension zone where Europe and Asia are being pulled apart. It is the northern extension of the spreading center in the Red Sea.

Pull-apart basins are growing in the overlaps of the Dead Sea transform fault zone.

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. Wetlands stop surface waves but not if they are filled in. This filling-in allows waves to reach more buildings than they would have otherwise. Water in the sediment is forced out and up into homes, causing flooding in lowest floors. Filled wetlands combine S and P waves into the more hazardous T waves.

Shaking is amplified, and deformation or liquefaction of the ground supporting the buildings can occur.

Which of the following accurately describe the tectonic boundaries of the Pacific plate? ___ The Pacific plate is created and spreads out from Hawaii and other hot spots in the central Pacific. ___ Smaller earthquakes occur at its spreading centers. ___ The Pacific Plate subducts along its northern and western edges. ___ 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. Slide-past motions dominate in the northeast Pacific and along its eastern border with California.

Which of the following factors contributed to the damage caused by earthquakes in the San Francisco Bay region? Building heights that did not match the period of the earthquakes Soft mud and artificial fill used in many areas amplified shaking. Poorly built older buildings made of unreinforced masonry or brick-facade construction The practice of anchoring some buildings to the bedrock instead of floating them on soft sediment that can absorb some of the energy

Soft mud and artificial fill used in many areas amplified shaking. Poorly built older buildings made of unreinforced masonry or brick-facade construction

Which type of tectonic setting listed below has the largest number of strong earthquakes? Interplate areas Transform plate boundaries Subduction zones Spreading centers

Subduction zones

Which of the following are transform plate boundary faults? The Alpine fault of New Zealand The San Andreas fault in California The Enriquillo-Plantain Garden fault in Haiti The Tokai fault of Japan

The Alpine fault of New Zealand The San Andreas fault in California The Enriquillo-Plantain Garden fault in Haiti

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? A triple junction has developed in the San Francisco Bay area that is causing extension to the north, west, and south toward Baja California. The western push of North America into Pacific Ocean crust resulted in the formation of a subduction zone offshore of California. The uplift of the Sierra Nevada Mountains has caused the downdrop of coastal California, resulting in normal faulting. 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 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.

What is causing the earthquakes in the region of India, China, and Pakistan? Volcanoes related to an ancient subduction zone Asia's subduction under the advancing India plate The India plate's push into Asia The weight of the water behind the new dams in the region

The India plate's push into Asia

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. The increasing mass of the overlying water changes the nature of the earthquakes when they happen at greater depths. The force of gravity changes with depth. The rocks lose heat gained from the atmosphere as they descend, and that changes their resistance to stress.

The forces that cause earthquakes align differently with depth, and the rock's resistance to stress changes with depth.

How are earthquakes named? Earthquakes are named after the town the farthest away from the epicenter to experience ground movements. The name is taken from the most prominent geographic feature near the epicenter. A committee produces a list of names each year that are sequentially used as earthquakes occur. The scientist to first record seismic waves from the earthquake is given the right to name the event.

The name is taken from the most prominent geographic feature near the epicenter.

Why do subduction zones result in earthquakes with the greatest magnitudes? ___ Earthquakes waves have their amplitudes magnified in convergent zones. ___ They are the only type of plate boundary where true faulting occurs. ___ The types of rocks found in convergent zones are the most resistant to stress. ___ The process of subducting a tectonic slab or pushing two continents together requires incredible amounts of energy.

The process of subducting a tectonic slab or pushing two continents together requires incredible amounts of energy.

What is the reason divergent boundaries have fewer earthquakes than other boundaries? ___ They are located in the shadow zones where seismic waves cannot travel. ___ They tend to occur in the deep ocean where the pressure of the overlying water dampens earthquake frequency. ___ The rocks located there are warmer, which prevents them from building up a lot of stored stress. ___ They have lower rates of plate motion.

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 Arabian plate is pulling away from the Eurasian plate, causing extensional faulting. ___ The Arabian plate is being uplift in the middle by a pool of magma, causing it to slide into Asia. ___ The Arabian plate is being subducted under the Eurasian plate. ___ The spreading centers that formed the Arabian plate are pushing it into Eurasia, causing collision uplifts.

The spreading centers that formed the Arabian plate are pushing it into Eurasia, causing collision uplifts.

Which of the following are the projections for earthquakes in the San Francisco Bay region? (Select all that apply.) There is a 52 to 72% chance that a 6.7 magnitude earthquake will occur in an urban area before 2032. There is a 80% chance that the San Andreas fault system will not experience another earthquake before 2032. There is a 27% chance the Hayward fault will cause a magnitude 6.7 or greater earthquake before 2032. There is a 65% chance the Hayward fault will cause a magnitude 9.1 or greater fault before 2032.

There is a 52 to 72% chance that a 6.7 magnitude earthquake will occur in an urban area before 2032. There is a 27% chance the Hayward fault will cause a magnitude 6.7 or greater earthquake before 2032.

Which of the following has been observed as a pattern in the progression of earthquakes along faults in the San Francisco Bay region? Earthquakes seem to alternate the end of the fault they occur on. There seems to be a southern progression of earthquakes along faults. There seems to be a northward progression of earthquakes along faults. Faults seem to be break from the middle outward toward both ends.

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. Shaking caused by the earthquake triggers explosions in the gas tanks of the cars. Cars are often all rolled in one direction and knock out the walls as they impact them. It slows the evacuation of buildings as earthquakes occur because people are reluctant to leave their cars behind.

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? They accelerate fires burning in the aftermath of earthquakes due to a flammable chemical used to make them. They are supported by flimsy concrete columns that fail in earthquakes. They are weak in earthquakes. They are heavy.

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 on the slabs with enough heat to provide the energy needed to power a large earthquake. ___ The interiors are the only parts of the slabs that descend beyond the first 100 km as the rest melts away. ___ They are the only places left on the descending slabs still cold enough to resist the pressures before breaking in a rigid manner.

They are the only places left on the descending slabs still cold enough to resist the pressures before breaking in a rigid manner.

True or false? Some of the earthquakes in the San Francisco Bay area seem to occur in pairs.

True

What is the tectonic setting of Haiti? Haiti is being pushed upward as two small continental landmasses are being pushed together by nearby spreading centers. Two parallel, east-west trending transform faults pass through Haiti where it sits at the northern edge of the Caribbean plate. A large subduction zone fault runs just south of Haiti as the Caribbean plate subducts under the Cocos plate. A spreading center runs north-south through Haiti that is creating an new ocean basin.

Two parallel, east-west trending transform faults pass through Haiti where it sits at the northern edge of the Caribbean plate.

The San Andreas fault is described as "locked" in the area of San Francisco. What does this mean for the fault? It is slowly slipping a bit each year, and so large earthquakes are effectively locked out of this section of the fault for the near future. Virtually all the tectonic stress is stored as elastic strain that will only be reduced in a big earthquake when the fault finally breaks. The fault has essentially been sealed over by magma.

Virtually all the tectonic stress is stored as elastic strain that will only be reduced in a big earthquake when the fault finally breaks.

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 divergent boundaries transform faults interplate locations

convergent boundaries

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 increases; increases decreases; increases increases; decreases

decreases; decreases

The locations where ruptures in Earth's crust occur as two sides move past each other in earthquake-generating events are called ______. faults cuts plates gaps

faults

Most earthquakes that occur along fracture zones between segments of midocean ridge occur ______. ___ on the segments outside the zone between the offset sections of ridge crest ___ on the segments between offset sections of ridge crest ___ along the entire length of the fracture zones

on the segments between offset sections of ridge crest

Most present-day earthquakes occur around the edge of the ____ Ocean.

pacific

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

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. fault-interlude seismic-gap California Long Beach

seismic-gap

At transform plate boundaries, tectonic plates on either side ______ each other. move toward move away from slide past

slide past

Subduction-zone earthquakes are ______. ___ unique in that they only produce surface waves ___ powerful enough to shake small buildings but not powerful enough to cause real damage ___ sometimes extremely powerful ___ barely detectable at the Earth's surface

sometimes extremely powerful

Small earthquakes too weak to knock over buildings or cause fatalities are most likely located at ______. spreading centers transform faults interplate faults subduction zones

spreading centers