Exam 2 Chapter 9 – Flashcards
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Which of the following describes the type of deformation experienced by rocks before an earthquake?
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slow deformation
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How are elastic rebound and elastic deformation different?
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Elastic deformation causes objects to bend, whereas rebound causes objects to return to their original shape.
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Elastic deformation before an earthquake is like _______, whereas rupture is like__________.
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stretching a rubber band; breaking a rubber band
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What will happen to a straight fence that undergoes elastic strain during an earthquake?
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The fence will bend in the direction of stress.
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What is a seismograph?
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an instrument used to record earthquake waves
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What is the underlying principle of seismograph construction?
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A heavy weight suspended within a moving box needs to overcome inertia, resulting in a slight delay in the motion of the weight after the box moves.
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When will the first earthquake waves arrive at a seismograph station?
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How long does it typically take for the first earthquake waves to arrive at a seismograph after the earthquake occurs?
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Which of the following is a characteristic of an S wave?
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"shaking" particle motion at right angles to the direction of wave travel
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What best describes the movement of P waves?
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compression and expansion
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Amongst all seismic waves, surface waves __________.
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have the slowest velocity
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The names primary and secondary refer to ___________.
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wave speed
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Which of the following correctly compares the seismograph readings from Station 1 to Station 2, as shown in the video?
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Surface waves show smaller amplitude at Station 2.
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According to the animation, what are the four primary zones in Earth's interior?
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crust, mantle, outer core, inner core
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What data provided information about the existence of different zones within Earth?
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P-wave and S-wave arrival times
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Which of the following statements about seismic wave ray paths is most accurate?
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Seismic waves move along curved ray paths because the properties of materials in the Earth change.
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Why do we believe Earth's outer core is a liquid?
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-S waves do not travel through the outer core.
- P waves slow down and refract at the boundary between the mantle and the outer core.
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Why do geologists believe the inner core is solid?
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P waves refract at the boundary between the outer core and inner core.
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How could you test whether the core of another planet were completely solid?
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Set off a bomb to create seismic waves. If S waves arrive on the opposite side of the planet, then the core is solid.
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Which of the following responses best describes the epicenter of an earthquake?
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The point on Earth's surface directly above the focus of an earthquake.
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In calculating the location of the epicenter of an earthquake, which of the following factors is most useful?
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the difference in arrival time of P and S waves
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In addition to a travel-time graph, at least how many seismograph stations are needed to determine the location of the epicenter of an earthquake?
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three
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As the distance between the epicenter of an earthquake and a seismograph station increases, so does the difference in the arrival times of the P and S waves. What causes this?
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P waves are faster than S waves.
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Which statement provides the best explanation of why most earthquakes occur at plate boundaries?
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Plate boundaries are locations on Earth where portions of the lithosphere interact as they move past each other.
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Define earthquake intensity.
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A qualitative measure of the amount of ground shaking at a certain location.
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A smaller earthquake in Virginia was felt over a larger distance, as compared to a larger earthquake in California. What is a reason this occurred?
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colder crust
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Richter magnitude (ML) is derived from measuring __________ and __________, and then plotting them on a Richter diagram.
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S minus P wave time; maximum S wave height
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Why is moment magnitude (MW) preferred over Richter magnitude (ML)?
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Moment magnitude measures the total energy released during an earthquake and can adequately measure the energy of large earthquakes.
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Which of the following best describes liquefaction?
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the transformation of stable soil into loose, liquefied material that is able to rise toward Earth's surface
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Describe how sand volcanoes form.
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An earthquake causes loose, saturated sandy material to liquefy, shoot upward through fractures of a confining unit, and eventually erupt at the surface.
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__________ in the sandy layer causes the ground to subside after sand volcanoes form.
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Tighter packing
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Structures built on __________ will become unstable during an earthquake.
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loose, saturated sediments
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A tsunami is caused by __________.
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anything that displaces water
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A __________ is located at a plate boundary between a subducting slab of oceanic crust and an overlying plate.
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megathrust fault
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What happens to tsunami waves as they move closer to shore?
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Velocity decreases and height increases.
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Which of the following locations on the Circum-Pacific Belt are likely to generate a tsunami?
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west coast of South America
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__________ is a seismic zone that has not produced a large earthquake for a considerable length of time.
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A seismic gap
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What are seismic gaps?
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Seismic gaps are unusually quiet zones along known active faults.
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Which earthquake was accompanied by extensive fire damage from ruptured natural gas lines and electrical lines?
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San Francisco, 1906
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What city in central United States was struck by three major earthquakes during the winter and spring months of the years 1811-1812 and experienced a quake as recently as 2008?
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New Madrid, Missouri
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Which type of wave moves the fastest and thus will reach the seismograph first?
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Primary Waves
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Why was building damage so extensive in the 1985 Mexico City earthquake?
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Much of the city is built on filled-in, shallow lakes and swampland.
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The __________ is the point of origination for an earthquake.
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focus
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What is the name given to material that loses all internal cohesion during earthquake shaking?
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Liquefaction
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Which one of the following statements concerning foci and epicenters is correct?
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The epicenter is at the surface directly above the focus, which is where the earthquake occurs.
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What is the direct measure of the distance from a seismic receiving station to the focus of a distant earthquake?
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The time interval between the arrivals of the first P and S waves
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Which of the following foundation materials is most stable during earthquake shaking?
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Bedrock
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How does the Mercalli Scale rate earthquakes?
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I to XII, ranging from little damage to total destruction
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What is the maximum possible damage designation on the Mercalli scale?
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There is total damage; objects are thrown into the air.
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Which one of the following statements is correct?
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S waves travel through solids and P waves travel through solids and liquids
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What is the most widely accepted explanation for the mechanism that generates earthquakes?
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Reid's elastic rebound theory
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The __________ is used to record ground shaking and the earthquake-magnitude scale was invented by __________.
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seismograph; Richter
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What type of waves will show the highest amplitudes on a typical seismogram?
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Surface waves
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Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with magnitude 5.5?
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32 times
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Which one of the following is true regarding tsunami?
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They occur in the open ocean; their wavelengths are many miles or kilometers and their wave heights are only a few feet.
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What factor produces the largest lateral ground displacement in an earthquake?
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Horizontally vibrating surface waves
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Why was the Marina District of San Francisco heavily damaged in the 1906 earthquake and the 1989 Loma Prieta quake?
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Liquefaction and foundation failures were common.
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Which of the following is directly related to the Richter earthquake-magnitude rating?
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Amplitude of the seismic waves
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The elastic rebound theory for the origin of earthquakes was first proposed by __________ following the __________ earthquake.
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Reid; 1906 San Francisco
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Why did the 1988 Armenian earthquake (in the Armenian Republic, then part of the former Soviet Union) result in an estimated 25,000 deaths?
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Numerous, poorly constructed, top-heavy concrete slab buildings collapsed.
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Which one of the following best characterizes tsunami?
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They have relatively small amplitudes compared to their very long wavelengths.
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Which of the following situations would result in the largest area of ground-shaking damage?
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A shallow-focus quake along the Mississippi Valley fault zone
