Geology Quiz Answers Chapter 12

Chapter 12: ● An earthquake is ______. ○ the sudden release of energy stored in rocks ● An earthquake is generated at a location we call the ______ and releases energy in the form of _______ waves (use the general term that includes all of the wave types). ○ Hypocenter or focus ○ Seismic ● Most earthquakes are generated by movement along faults. Match the fault type with its image. ● ● ● ● ● ○ ○ Left ■ Normal fault ○ Middle ■ Reverse fault ○ Right ■ Strike-slip fault Explosive eruptions, landslides, magma movement, and faulting are the causes of earthquakes associated with ○ Volcanoes Landslides generate seismic waves by ______. ○ causing the ground to shake The sudden release of energy stored in rocks causes a(n) ○ Earthquake Elastic behavior is when ______. ○ rocks return to their original shape after being strained Match the earthquake term with its correct description. ○ Seismic wave ■ Mode of earthquake energy transmission through Earth ○ Seismic station ■ Location of scientific instruments that measure earthquakes ○ Epicenter ■ Point on Earth's surface directly above where an earthquake is generated ● ● ● ● ● ○ Hypocenter ■ Location where an earthquake is generated Match the fault type with its appropriate description. ○ Normal faults ■ The hanging wall moves down with respect to the footwall; most common along divergent boundaries ○ Reverse faults ■ The hanging wall moves up with respect to the footwall; most common along convergent plate boundaries ○ Thrust faults ■ Gently dipping faults in which the hanging wall moves up with respect to the footwall; most common along convergent plate boundaries ○ Strike-slip faults ■ Two sides of the fault move horizontally past one another; fault plane is near vertical; most common along transform plate boundaries True or false: When an earthquake occurs along a fault, the entire plane of the fault slips at once. ○ False ■ An earthquake rupture starts in a small area (hypocenter) and expands along the fault over time. Volcanoes and magma generate earthquakes in which of the following ways? ○ Movement of magma within the volcano ○ Landslides on unstable slopes ○ Explosive eruptions Most earthquakes occur along ______. ○ plate boundaries Based on the map, what is true regarding earthquakes in the locations indicated? (Yellow dots = shallow-depth earthquakes; green dots = intermediate; red dots = deep.) ○ ○ A ■ Mostly shallow earthquakes occur along the mid-ocean ridge. ○ B ■ This is a diffuse zone of seismic activity associated with continental rifting ○ C ■ This is a large zone of seismicity associated with a continental collision. ○ D ■ Shallow, intermediate, and deep earthquakes occur along a subduction zone ○ E ■ Very little seismicity occurs in this area, which is far from a plate boundary ● Based on the map, which are true of the subduction zone and indicated earthquakes? (Yellow dots = shallow-depth earthquakes; green dots = intermediate; red dots = deep.) ● ● ● ● ○ ○ Shallow earthquakes are closer to the trench, whereas deep ones are farther away. ○ The subducted plate is generally inclined from west to east, with the deepest portion of the slab to the east. Rank the following in order from the start (at the top) of an earthquake rupture to the end of the earthquake event. ○ A small section of the fault begins to rupture ○ Rupture migrates outwards, generally following the actual fault surface ○ Rupture eventually may tech Earth's Surface, creating a fault scarp ○ Rupture grows along the fault plane, and fault scarp lengthens ○ Earthquakes stops as remaining stress no longer overcomes friction along the fault Which of the following are true of earthquakes related to mid-ocean ridges? ○ They may be due to strike-slip motion along transform faults. ○ They may occur along steep faults away from the ridge axis as the new crust cools and bends. ○ Many occur along the axis of the ridge due to normal faulting or magma intrusions. ○ Most have hypocenters less than 20 km deep. Megathrust earthquakes are characterized as ______. ○ large in magnitude ○ the most damaging and deadly Based upon the image that shows colored dots to represent earthquake epicenters, which are true of the locations of earthquakes? ○ ○ Most earthquakes occur along plate boundaries. ○ A few earthquakes occur far away from plate boundaries. ● Match the location on the image with the best description for causes of earthquakes in that location. ○ ○ A ■ Thrust faults form near the plate boundary and create large, shallow earthquakes. ○ B ■ Megathrust forms along the plate boundary and creates large earthquakes between the two plates ○ C ■ Thrust faults or reactivated older faults may form within the interior of either continent ○ D ■ Oceanic plate material is detached, and deep earthquakes cease. ● What is true regarding earthquakes in the locations indicated? (Yellow dots = shallow-depth earthquakes; green dots = intermediate; red dots = deep.) ○ ○ A ■ Subduction zone causes earthquakes along the Aleutian Islands. ○ B ■ Most earthquakes occur due to volcanic activity. ○ C ■ Strike-slip earthquakes are common along the San Andreas fault. ○ D ■ Shallow earthquakes follow the Mid-Atlantic Ridge. ○ E ■ Shallow, intermediate, and deep earthquakes occur along this subduction zone ● Match the location with the best description for earthquakes formed in that area within a continent. ○ ○ A ■ Strike-slip motion mostly causes shallow earthquakes; some may be large. ○ B ■ Moderate-size normal-fault earthquakes are created at a rift. ○ C ■ Magma intrusions may cause small earthquakes as molten material moves through rock ○ D ■ Preexisting faults readjust and move as the plate is subjected to new stresses; may produce large earthquakes. ● The direction of subduction indicated in the circular area is to the ______. ○ ○ Northwest ● The energy released by an earthquake travels through rocks as ______. ○ seismic waves ● Match the location on the image with the best description for causes of earthquakes in that location. ○ ○ A ■ Rocks along this linear feature flow because they are too hot to fracture; earthquakes are shallow, small, and numerous. ○ B ■ Strike-slip earthquakes occur along faults that link adjacent segments of the spreading center. ○ C ■ Plate cools, subsides, and bends as it moves away from the ridge; stress from the bending forms steep faults ○ D ■ Spreading and slip between adjacent blocks occurs along normal faults; earthquakes occur as magma intrudes into fissures ● Which of the following are true for seismic waves? ● ● ● ● ● ● ○ Body waves include P-waves and S-waves. ○ Body waves travel within and through Earth. ○ Surface waves only travel on the surface of Earth. ■ Primary waves, a type of body wave, are the fastest of the seismic waves. ■ Surface waves are Love and Rayleigh waves. ■ Both types of body waves, P- and S-waves, can travel through solids. Representing the huge thrust fault created by subduction, ______ earthquakes are deadly and damaging, and commonly create tsunamis. ○ Megathrust Seismic waves are recorded by a digital instrument called a ______ and may be viewed either on a computer screen or as a paper plot printout called a ______. ○ seismometer; seismogram Which of the following are true of earthquakes related to continental collisions? ○ They may occur in either continental plate. ○ They may occur in large thrust faults created near the plate boundary. ○ A megathrust between the two plates creates large earthquakes. ○ Earthquakes are widely distributed along the collision zone. ■ Very little magma is created at this type of plate boundary ■ Most earthquakes here are shallow in depth. In which of the following ways may earthquakes be generated within a continental plate? ○ Continental rifting and normal faulting ○ Intrusions of magma ○ Transform faults ○ Movement of preexisting faults subjected to new stresses Rank seismic waves in order of recording by a seismometer (from first to last). ○ P-wave ○ S-wave ○ Surface wave Based on the three seismograms, which seismic station was closest to the epicenter of the earthquake? ○ ○ ISCO ● The two basic types of seismic waves include ______ waves, which are created when seismic wave energy reaches Earth's surface and is transformed into new horizontal and vertical waves, and ______ waves, which are usually generated at faults and travel through Earth (primary and secondary). ○ surface; body ● Which are true of "Richter" or "local" magnitude calculations? ○ Use maximum S-wave amplitude on a seismogram ○ Most commonly mentioned ○ Use a nomograph to relate distance, magnitude, and amplitude ● A seismometer ______. ○ detects and records ground motion during earthquakes ○ is often placed with two others, oriented at 90o to detect three components of motion ○ may create a graphic plot called a seismogram ■ One seismograph contains three seismometers to measure all directions of motion. ■ A seismogram is created by a seismometer. ● Which location on the image experienced the most shaking intensity (extensive damage), according to the Modified Mercalli Intensity Scale? ○ ○ D ● Match the location on the seismogram with the appropriate description. ○ ○ D ■ Background vibrations ○ A ■ Arrival of first P-waves ○ C ■ Arrival of first S-waves ○ B ■ Arrival of first surface waves ● Flooding because of dam failures, flooding due to subsidence, and rupturing gas lines are ______ due to earthquakes, whereas shaking of structures and buildings, liquefaction, and the destruction of structures by faulting are ______ due to earthquakes. ○ secondary effects; direct damage ● If three seismic stations have the following P-S intervals: DUG = 57 sec, WUAZ = 73 sec, ISCO = 14 sec, place the stations in order from closest station (at the top) to the earthquake to the one farthest away. ○ ISCO ○ DUG ○ WUAZ ● Earthquakes, landslides, and volcanic eruptions that occur beneath the sea may generate a large sea wave called a ______. ○ Tsunami ● Rank the following in order for the steps taken to measure the local magnitude (Ml) of a shallow earthquake. Place the first step on top ○ seismic data are gathered from several seisometers ○ maximum amplitude of the S-wave is measured on each seismogram ○ relationships between distance and S-wave amplitude are plotted on a nomograph ○ MI is the point where each line crosses the center column of the nomograph ● List the order of events, from first (on top) to last, that would lead to the formation of a tsunami due to an earthquake. ○ Megathrust is locked, causing the seafloor to bulge under stress. ○ Megathrust ruptures, and bulging plate changes shape. ○ Water above the plate lifts up toward the surface, forming a ridge of higher water. ○ A tsunami radiates away from the disturbance; not noticeable in the open ocean. ○ Tsunami approaches shore; energy concentrates in shallows to create a higher wave. ● Which fault, located in California, is both the world's best known and extensively studied? This fault is found along a transform plate boundary and will likely produce a significant earthquake in the next 30 years. ○ San Andreas ● Which are true of the Modified Mercalli Intensity Scale? ○ A value of XII indicates complete destruction of buildings. ○ It describes the effects of shaking in everyday terms. ○ It may be used to describe earthquakes that occurred before seismometers were invented. ■ The Mercalli Scale uses Roman numerals. ■ The Richter and moment magnitude scales report magnitude. ■ The Richter and moment magnitude scales use S-wave amplitudes. ● Which of the following are potential sources of destruction that may be caused either directly or secondarily by earthquakes? ○ Aftershocks ○ Landslides and rock falls ○ Fires ○ Tsunamis ● Tsunamis may be generated by ______. ○ activity associated with volcanic eruptions ○ landslides that displace large amounts of water ○ earthquakes that cause the seafloor to shift ● Which of the following describe the San Andreas fault? ○ It is located along the boundary between the North American plate and the Pacific plate. ○ It is made of different segments that have different tectonic behaviors. ○ It is located in California. ■ The San Andreas marks a transform plate boundary. ■ Many large and small earthquakes have occurred along the fault in the past 100+ years.