INSTANT DOWNLOAD COMPLETE TEST BANK WITH ANSWERS
Natural Hazards And Disasters 4th Edition by Donald Hyndman – Test Bank
EARTHQUAKES AND THEIR CAUSES
- What is the approximate highest frequency of vibration (of back and forth shaking) in earthquakes?
- 2-3 cycles per minute
- 2-3 cycles per second
c. 20-30 cycles per second
- 2,000-3,000 cycles per second
- 20,000-30,000 cycles per second
2. Which type of earthquake waves shake with the largest amplitudes (largest range of motion)?
- compressional waves
- shear waves
c. surface waves
- P waves
- S waves
3. How is the distance to the source of an earthquake determined?
- by calling many seismograph operators to see who felt it most strongly
b. by subtracting the travel times of P and S waves
- by measuring the frequency of the P waves as they arrive at a seismograph
- by measuring the height of the S waves recorded on a seismograph
- by adding the travel times of the L waves and the Raleigh waves
4. What does the Richter Magnitude Scale depend on?
a. the maximum amplitude of earthquake waves on a seismograph
- the frequency of P waves recorded on a seismograph
- the intensity of shaking during the earthquake
- the amount of destruction by the earthquake
- the distance to the earthquake focus
5. A magnitude 7 earthquake has how much higher ground motion than a magnitude 6 earthquake on a seismogram?
a. twice as high
b. 10 times higher
- 32 times higher
- about 100 times higher
- about 1,000 times higher
6. Which type or types of earthquake waves move only near the surface of the Earth?
a. all earthquake waves
b. P waves
c. surface waves
d. S waves
e. waves from faults that break near-surface rocks
- What kind of material is subject to liquefaction during an earthquake?
- clay saturated with saltwater
- soils that are not saturated with water
- swelling clay saturated with water
- loose sand grains with water between the grains
- poorly compacted artificial fill dumped into the edge of a bay to add usable land
8. What does the Mercalli Intensity Scale depend on?
a. how much damage occurred in an area
b. the intensity of shaking of the seismograph
c. the amplitude of movement of the seismograph needle
d. the strength of rocks broken along the fault
e. the frequency of the earthquake waves as they reach the seismograph
- Why do parking garages often fail and fall during an earthquake?
- Garages fall due to a lack of steel reinforcing bars.
- Garages are made of poor quality concrete.
- Horizontal spans across the large openings are too long to support the weight of vehicles.
- Horizontal support beams shake off their vertical columns because they are often not well braced.
- The vertical concrete supports are too thin to support the load.
10. What is the approximate P-wave velocity through the Earth’s mantle?
a. 8 meters per second
b. 80 meters per second
c. 8 kilometers per second
d. 80 kilometers per second
e. 800 kilometers per second
11. Which type or types of earthquake waves arrive at a distant seismograph most quickly by traveling by moving through the mantle of the Earth?
a. both P and S waves
b. both P and L waves
c. both S and L waves
d. only S waves
e. only P waves
12. Which types of earthquake waves do the most damage?
a. compressional waves
b. shear waves
c. body waves
d. P waves
e. surface waves
13. Which earthquake waves arrive first?
a. P waves
b. S waves
c. L waves
d. shear waves
e. surface waves
14. Which earthquake waves arrive from the source last?
a. P waves
b. S waves
c. surface waves
d. shear waves
e. body waves
15. Why are surface waves the most destructive type of earthquake waves to buildings?
a. They are compressional waves.
b. They are shear waves.
c. They first compress the material and then pull it apart.
d. They move with the highest velocities.
e. They have larger amplitudes of shaking.
16. Which waves have the lowest frequencies?
a. P waves
b. S waves
c. surface waves
d. compressional waves
e. shear waves
17. How much more energy is released in a magnitude 7 earthquake than in a magnitude 6 earthquake?
a. about double
b. about 3 times
c. about 10 times
d. about 32 times
e. about 100 times
18. Moment magnitude depends on what main factor(s)?
a. total offset distance on the fault during the earthquake
b. total length of the fault ruptured
c. shear strength of the rocks displaced, total surface area of rocks ruptured, and average slip distance on the fault
d. frequency of movement of the earthquake waves and the total time of shaking
e. amplitude of seismograph swing at the first moment of arrival of shaking
19. Between magnitude 7 and magnitude 8 earthquakes, about how much harder is the shaking (how much increase in the acceleration of the ground)?
a. actually less acceleration because the frequency is lower
b. not much
c. twice as hard
d. about 10 times
e. about 32 times
20. If you find a well-exposed fault that moved before seismographs were available, you can infer the approximate magnitude of earthquake by measuring the:
a. largest size tree snapped off by the shaking.
b. average size of the largest rocks moved in the earthquake.
c. strength of the rocks that the earthquake managed to break.
d. total area affected by the tsunami wave produced by the event.
e. total length of fault break during the event.
SHORT ANSWER QUESTIONS
- Where a tall building is right next to a short building, why is the tall building often damaged? Why does the damage occur and where in the building?
ANSWER: Tall buildings sway more slowly than short buildings, so the buildings bang into one another. The tall building breaks at the top of the short building.
- Name the three main types of earthquake waves.
ANSWER: Primary (P), secondary (S), and surface waves.
3. What is the approximate P-wave velocity through the Earth? Indicate whether your answer refers to the Earth’s crust or mantle.
ANSWER: 5-6 km/sec in continental crust; 8 km/sec in mantle.
4. Which type or types of earthquake waves arrive at a distant seismograph most quickly by traveling through the mantle of the Earth?
ANSWER: P and S waves.
5. Why are surface waves the most destructive type of earthquake waves (two different reasons)?
ANSWER: Larger amplitude of shaking (greatest ground motion). Closer to surface of earth and thus closer to buildings.
6. How much more energy is released in a magnitude 7 earthquake than in a magnitude 6 earthquake?
ANSWER: About 32 times.
7. In addition to the amount of damage, increases in what factors go along with an increase in earthquake magnitude? List several.
ANSWER: Fault offset; length of fault ruptured; acceleration of the ground; time of shaking; velocity of motion of the ground.
- What hazard does liquefaction pose, and for who or what?
ANSWER: Differential settling of the ground can collapse or topple buildings on people.
- Sometimes a single floor of a tall building (above ground floor) collapses in an earthquake even though the floors have identical construction. Why?
ANSWER: The frequency of shaking of the ground matches the frequency of shaking of the building.
- What is meant by a blind thrust? Provide an example of an earthquake along a blind thrust.
ANSWER: A blind thrust is a low angle reverse fault that does not rupture the Earth’s surface during an earthquake. The 1994 Northridge, California earthquake occurred due to displacement on a blind thrust.
CRITICAL THINKING ESSAY QUESTIONS
- Explain the ways in which devastation from an earthquake could be minimized in a community.
ANSWER: Earthquake devastation could be minimized beforehand by better building methods and by having an effective and efficient emergency response plan for communities that are likely to experience earthquakes.
- Which type of plate boundary has the potential to cause the most destructive earthquakes??
ANSWER: The largest earthquakes recorded have occurred at subduction zones.
- Where do earthquakes typically occur? Explain why they occur where they do. Which coast of North America has highly damaging earthquakes that are less frequent?
ANSWER: Earthquakes typically occur at plate boundaries, and they occur as a result of the gradual buildup of strain due to convection currents in the asthenosphere moving tectonic plates in different directions. The west coast of North America, especially Alaska, has highly damaging earthquakes that are less frequent. The Pacific Northwest also receives highly damaging earthquakes as a result of the Juan de Fuca plate subducting under the North American plate.
- Discuss the types of earthquake waves and the potential damage each individual one can cause.
ANSWER: P waves hit first; they are the least damaging and manifest themselves as compressional waves. S waves, or shear waves, hit next; they are moderately damaging and are waves where a back-and-forth motion is detected perpendicular to the land surface. Surface waves are the most damaging, and they hit last. They are the boundary between two media with different physical properties, and they are responsible for most damage in earthquakes.
- Discuss the effects of liquefaction, landsliding, and clay flake collapse on society.
ANSWER: Liquefaction causes a land surface to behave as a liquid, and buildings sink into the mud. Landsliding causes buildings to move downslope. Clay flake collapse causes erosion that undermines the stability of buildings. All three types of movement are capable of causing massive damage to buildings, which are built on top of this substrate, and present serious engineering challenges to society.
SINKHOLES, LAND SUBSIDENCE, AND SWELLING SOILS
- What causes sinkhole collapse? Where is the cavity that it collapses into, and how does that cavity form?
a. A limestone cavern dissolves out with acid rain; a sinkhole forms when its roof collapses.
b. Soil above a limestone cavern percolates down into the cavern, leaving a soil cavity above. That cavity may collapse to form a sinkhole.
c. An underground river erodes a wide area; a sinkhole forms if its roof collapses.
d. The roof of a gold or copper mine collapses to form a sinkhole.
e. Families of moles or gophers dig large underground chambers that can collapse to form sinkholes.
- What causes caverns in limestone?
a. Hard grains of quartz sand carried in underground streams erode the soft limestone.
b. They form when rocks above collapse into the limestone.
c. Limestone readily dissolves in seawater, so the caverns formed originally at sea level.
d. Groundwater in limestone is somewhat caustic, so over many years, it dissolves limestone.
e. Rainwater dissolves carbon dioxide to make weak carbonic acid that dissolves limestone.
- Where in North America are sinkholes most prevalent and why?
a. in Michigan, because outcrops of limestone are widespread and it is surrounded by the Great Lakes
b. in Washington state, because of all of the rain west of the Cascades
c. in metamorphic rocks of the Canadian Shield, because of all of the lakes
d. in Florida, because it is almost all limestone and has abundant groundwater
e. in Colorado, because layers of sedimentary rocks under the Great Plains bend up to the surface there
ANSWER: d [FIGURE 9-6]
- What is karst and how does it form?
a. Karst is the ragged surface dissolved on the surface of limestone bedrock formerly buried under soil.
b. Karst is windblown dust deposited in areas of dune-like hills.
c. Karst is the deposit of calcium carbonate that precipitates on rocks in soil when groundwater evaporates.
d. Karst is the cold wind that blows off the North Atlantic Ocean at times in late fall.
e. Karst is the product of reaction between acid rain and limestone in the ground.
- What are the main characteristics of soil above a limestone cavern that leads to the formation of a cover collapse sinkhole?
a. thin enough that it can trickle through limestone cracks into a cavern below
b. sandy and loose enough that it can trickle down into cracks in limestone
c. coarse-enough grains that surface water can percolate down into cracks above a limestone cavern
d. fairly well cemented so it can maintain the roof of a cavern
e. thick, clay-rich, and cohesive enough to develop a large cavern before it collapses
- What weather conditions are most likely to foster the formation of sinkholes?
a. dry weather, because that dehydrates the soil, causing shrinkage and collapse
b. freezing weather, because freezing water expands, causing stresses that force fractures apart to collapse
c. dry weather, because that lowers the water table so the cavern roofs are not supported and may collapse
d. wet weather, because there is ample water to dissolve out caverns
e. wet weather, because the pressure of water in a cavern causes stress that can weaken and collapse the roof
- Other than limestone, what other types of rocks are soluble and can form cavities that collapse?
a. salt and shale
b. shale and bauxite
c. salt and gypsum
d. kaolinite and smectite
e. smectite and gypsum
- Which of the following areas has NOT seen major subsidence from groundwater withdrawal?
a. San Joaquin Valley of California
b. Las Vegas area
c. Houston area, Texas
d. Charleston, South Carolina
e. Venice, Italy
ANSWER: d [Table 9-1]
- What causes swelling soils to swell?
a. When they get wet, water enters the clay mineral structure to cause swelling.
b. The presence of abundant kaolinite clay takes water in between its layers.
c. When water in clay-rich soil freezes, the soil swells.
d. When an earthquake shakes wet soil, more water can get between the grains to cause swelling.
e. Landsliding of a mass relieves pressure on soil, permitting it to expand.
- Which of the following does NOT lead to formation of sinkholes?
- strong pumping of groundwater for crop irrigation in dry weather
- pumping groundwater for spraying on crops to prevent freezing
- construction of a heavy building over a limestone cavern
- pumping waste fluids into the ground for disposal
- drilling for groundwater
11. Which is NOT a method for recognizing the presence of swelling soils?
a. They are extremely slippery when wet.
b. They form a popcorn-like surface when dried out.
c. They stick like gum to the bottom of your shoes when wet.
d. Since they deform elastically, the ground feels spongy or bouncy underfoot.
e. They deform concrete foundations and walls.
12. A roof made of what kind of material collapses to form a cover subsidence sinkhole?
- sandy and permeable sediment
- evaporate deposits of salt and gypsum
- solid limestone with a few fractures
- porous limestone with lots of fractures
- swelling soil
13. What is in water in the ground that helps it dissolve limestone?
- nitric acid from nitrogen in the air combining with rainwater
- carbonic acid formed from carbon dioxide in air combining with rainwater
- nothing—pure water has nothing in it, so it can dissolve more
- oxygen—the reactivity of oxygen oxidizes the calcium of limestone
- sand—the grains are much harder than limestone, making it more abrasive
14. How would you recognize a karst landscape?
a. Karst forms very rough deposits of calcium carbonate on various kinds of rock outcrops.
b. Karst forms a rather smooth, flat surface on limestone because of extensive solution by acid rain.
c. Karst has an extremely ragged surface dissolved on the surface of limestone bedrock.
d. Karst forms dune-like rounded hills of windblown dust.
e. Karst is the smooth surface formed on soft shales when salty sea spray reacts with them.
- Why does Venice, Italy, have canals for gondolas and boats instead of normal streets for cars?
- It was built on soft muds of a lagoon, and the heavy buildings settled into the mud.
- The smectite soils in muds under it lead to lateral spreading and subsidence under the load of buildings.
- The low ground next to the lagoon was a difficult place to provide a good road foundation.
- Since the city was built about 1,600 years ago, the sea level has risen.
- Extraction of groundwater below the city caused subsidence of the city below sea level.
- Why are there so many small lakes and springs in western Florida?
- Since the water table is essentially at the surface, any low area is filled with water.
- Limestone caverns and sinkholes filled with water because of the high water table.
- Groundwater rising through the limestone bedrock dissolves it as it reaches acid rain at the surface.
- Many of them are old limestone quarries, abundant there because of cheap transportation near the Gulf.
- A swarm of asteroids peppered the area a few thousand years ago; the holes have since filled with water.
- Under what weather conditions are sinkholes most likely to form?
- low pressure under the eye of a hurricane
- especially dry season
- especially wet season
- El Niño
- freezing weather
18. In the United States, sinkholes, subsidence, and swelling soils cause total dollar damage at which of the following levels?
a. more than earthquakes and volcanoes
b. more than hurricanes but less than floods
c. more than forest fires but less than floods
d. more than floods but less than landslides
e. less than hurricanes, floods, or landslides
19. Caves and caverns most commonly develop in:
20. Which of the following statements about sinkhole formation is incorrect?
- Cover collapse is a way that a sinkhole can form.
- Permafrost thaw is a way that a sinkhole can form.
- Large caverns generally form in limestone just below the water table.
- Cover subsidence is a way that a sinkhole can form.
- Sinkhole formation depends on the presence of soluble sedimentary rocks like limestone.
SHORT ANSWER QUESTIONS
1. What agricultural behavior is likely to lead to formation of more sinkholes?
ANSWER: Aggressive pumping of groundwater for crop irrigation or spraying on crops to prevent freezing. In both cases, pumping lowers the water table, removing roof support in caverns.
2. What aspects of construction can lead to the formation of sinkholes? Why?
ANSWER: Drilling of water wells or foundation test holes. A well-drilling truck can load the top of a cavity to cause collapse. Drilling a hole in the top of a cavern can weaken the roof and cause collapse.
3. What material causes swelling soils?
ANSWER: Smectite, the swelling clay.
4. How can you recognize the presence of swelling soils?
ANSWER: They are extremely slippery when wet; they form a popcorn-like surface when dried out.
5. What is bad about swelling soils?
ANSWER: Swelling deforms and cracks foundations, chimneys, walls, driveways, and roads; roads are extremely slippery when wet; landslides are more common.
6. What type of ground settling process is common in high latitudes?
ANSWER: Thawing of permafrost.
7. What is in water in the ground that helps it dissolve limestone? Where does that substance come from?
ANSWER: Carbonic acid; it forms from carbon dioxide in the air combining with rainwater.
8. Name three of the eight states with the largest areas of ground subsidence, including sinkholes.
ANSWER: Florida, Georgia, Texas, New Mexico, Kentucky, Tennessee, Virginia, and Missouri. [Figure 9-6]
9. What are two main mechanisms of ground subsidence?
ANSWER: Sinkholes, extraction of water or other fluids from sediments, and drainage of peat or other organic soils.
- What specific area of the western United States is noted for almost 9 meters of subsidence due to agriculture? Specifically what caused the subsidence?
ANSWER: The San Joaquin Valley (Great Valley of California); subsidence caused by extraction of groundwater for agriculture. [Table 9-1]
CRITICAL THINKING ESSAY QUESTIONS
1. Your friend just got back from vacation and wants to know if you can help him understand why the place he visited looked so weird. He describes the landscape as being uneven, with lots of depressions, and some ragged parts. What type of landscape is this? How does this type of landscape form? If your friend was on vacation in the United States, where are some of the places he could have been?
ANSWER: Karst; Mammoth Cave National Park in Kentucky, Florida, southwestern Missouri, southeastern states, the Appalachians, or western Texas.
2. Venice, Italy, is noted for numerous water canals instead of paved streets for cars. Why doesn’t it have many typical streets? Explain briefly.
ANSWER: Extraction of groundwater under the city caused subsidence and sinking of the city below sea level.
- What causes permafrost thaw? What are several problems associated with it? What is one way to overcome permafrost thaw?
ANSWER: Permafrost thaw occurs when increased atmospheric temperature warms the ground surface, causing water to melt and settling to occur as water in the previously supported pore spaces in between grains flows out; permafrost thaw causes landslides, upsets foundations of buildings and roadways, and promotes melting of Arctic sea ice; installing thermosiphons into the Trans-Alaska Pipeline, building strategies, and when building roads, covering the permafrost with crushed stone.
- In the case of Mexico City, Mexico, land subsidence due to unsustainable groundwater pumping caused many problems because the area is highly populated. Discuss two of these problems.
ANSWER: Buildings tilt; water lines crack or break, causing huge losses of potable water; sewer lines are damaged, causing sewage and contaminants to infiltrate the aquifer below; 24-hour pumping is needed to prevent summer rains from flooding the city; sometimes, water supplies are shut down to conserve them.
- Discuss the four causes of land subsidence described in the text and one case study of each cause.
ANSWER: Mining groundwater and petroleum (San Jose, Houston, or Wilmington/Long Beach); drainage of organic soils (San Joaquin Valley, Florida Everglades, Mississippi River delta, or the Netherlands); drying of clays (Leaning Tower of Pisa or Ottawa–St. Lawrence River lowland); thaw and ground settling (Trans-Alaska Pipeline).