Geology - Earthquakes Review ANSWERS
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GEOLOGY FINAL REVIEW Earthquakes
1.
Seismology and seismicity are both related to the study of earthquakes, but they have distinct focuses. What is the primary difference between these two terms according to the passage? A) Seismology deals with the internal structure of the Earth, while seismicity focuses on earthquake locations. (Incorrect - Seismology doesn't exclusively focus on internal structure) B) Seismology is the practical application of studying earthquakes, whereas seismicity is the theoretical underpinning. (Incorrect - Both involve scientific study) C) Seismology studies all types of waves traveling through the Earth, while seismicity is limited to earthquake-generated waves. (Incorrect - Seismology focuses on seismic waves, but not all Earth waves) D) Seismology is the scientific study of earthquakes and their effects, while seismicity refers to the actual occurrence and statistical distribution of earthquakes. (Correct Answer) E) Seismology focuses on predicting future earthquakes, and seismicity deals with past earthquake events. (Incorrect - While prediction is a goal, the passage talks about general study, not prediction) Explanation: The answer is (D) Seismology is the scientific study of earthquakes and their effects, while seismicity refers to the actual occurrence and statistical distribution of earthquakes. The passage clearly defines the two terms: ●
Seismology: The scientific study of earthquakes and the propagation (movement) of elastic seismic waves through the Earth. This field encompasses understanding earthquake causes, effects, and the properties of seismic waves. ●
Seismicity: The distribution of earthquakes in space, time, and magnitude. This refers to the actual statistical patterns of earthquake occurrences, including their location, frequency, and intensity. Seismology is the broader field that uses various tools and methods to study earthquakes and seismic waves. Seismicity is a specific aspect of seismology that focuses on the statistical patterns of earthquake occurrences themselves. 2.
Both the epicenter and hypocenter are crucial in understanding earthquakes. What is the key difference between these two terms? A) The epicenter is the deepest point within the Earth where the earthquake originates, while the hypocenter is the location on the surface directly above it. (Incorrect - Reverses the definitions) B) The epicenter is a scientific theory for earthquake origins, whereas the hypocenter is the actual location where the earthquake starts. (Incorrect - Both are based on real locations) C) The epicenter is the point of strongest ground shaking during an earthquake, and the hypocenter is the location deep within the Earth where the shaking originates. (Incorrect - Epicenter doesn't pinpoint strongest shaking, both relate to origin) D) The epicenter is the point on the Earth's surface directly above the hypocenter, which is the actual location where the earthquake rupture starts deep underground. (Correct Answer) E) The epicenter is a measurable value related to the earthquake's magnitude, and the hypocenter describes the type of fault that caused the earthquake. (Incorrect - Neither term relates directly to magnitude or fault type) Explanation: The answer is (D) The epicenter is the point on the Earth's surface directly above the hypocenter, which is the actual location where the earthquake rupture starts deep underground. The passage clearly defines the two terms: ●
Hypocenter (or focus): The actual location of the earthquake's initiation point deep within the Earth. This is where the fault rupture begins. ●
Epicenter: The point on the Earth's surface directly above the hypocenter. This essentially locates the earthquake's origin on the surface based on the hypocenter's location underground.
Understanding the distinction between these two points is crucial for studying earthquake epicenters and their corresponding areas of ground shaking and potential damage. 3.
Earthquakes are often associated with faults in the Earth's crust. Match the following descriptions to the three main types of faults: 1.
Two tectonic plates are moving ______, creating a rift valley or mid-ocean ridge. Earthquakes are common along these zones. (Fill in the blank: apart)
2.
Two tectonic plates are moving towards each other, with one plate often ______ (going under) the other. This can create mountain ranges, trenches, and volcanic activity. Earthquakes are frequent in these zones. (Fill in the blank: subducting)
3.
Two tectonic plates are sliding past each other ______. These faults do not involve plates moving apart or coming together, but they can still experience earthquakes. (Fill in the blank: horizontally)
Explanation:
1. Two tectonic plates are moving
apart,
creating a rift valley or mid-ocean ridge. Earthquakes are common along these zones. ●
Explanation: This describes divergent boundaries. As tectonic plates move away from each other, the Earth's crust stretches and thins, creating features like rift valleys and mid-ocean ridges. The movement and stress along these boundaries lead to frequent earthquakes. 2. Two tectonic plates are moving towards each other, with one plate often subducting
(going under) the other. This can create mountain ranges, trenches, and volcanic activity. Earthquakes are frequent in these zones. ●
Explanation: This describes convergent boundaries. When tectonic plates collide, one plate may be forced beneath the other, a process called subduction. This subduction can lead to the formation of mountain ranges, trenches, and volcanic activity. Convergent boundaries are zones of intense geological activity and frequent earthquakes. 3. Two tectonic plates are sliding past each other horizontally.
These faults do not involve plates moving apart or coming together, but they can still experience earthquakes. ●
Explanation: This describes transform faults. These faults occur where two plates slide past each other laterally, without converging or diverging. While they don't involve the large-scale movements of convergent or divergent boundaries, friction and stress build-up along transform faults can still cause earthquakes. 4. Where do the world's largest earthquakes typically occur, and what type of plate boundary is associated with this location? A) Mid-ocean ridges, where divergent boundaries form new oceanic crust. (Incorrect - Divergent boundaries are not known for large earthquakes) B) Transform faults, where plates slide past each other horizontally. (Incorrect - Transform faults can have large earthquakes, but not the largest) C) Subduction zones, convergent boundaries where one plate subducts beneath another. (Correct Answer) D) Hotspots, where plumes of hot mantle material rise and create volcanic activity. (Incorrect - Hotspots are not plate boundaries and don't typically cause large earthquakes) E) Continental collisions, where two continental plates push against each other, forming mountain ranges. (Incorrect - While these boundaries can have earthquakes, they are not the most common location for the largest ones) Explanation: The passage highlights subduction zones as the location for the world's largest earthquakes: ●
Megathrust earthquakes, the largest on Earth, occur at subduction zones. ●
Subduction zones involve convergent boundaries where one tectonic plate subducts beneath another.
●
The large size of these faults and the potential for a wider rupture zone on a gently dipping subduction zone contribute to the generation of massive earthquakes. The other answer choices describe different geological features or plate boundaries that are not typically associated with the largest earthquakes. 5. Based on historical records, in which three of the following regions have earthquakes occurred in Canada over the past 300 years? A) Atlantic Provinces (Newfoundland, Nova Scotia, Prince Edward Island, New Brunswick) (Correct Answer) B) Victoria Island, Nunavut (Incorrect - Victoria Island is not a region known for earthquakes in Canada) C) Southern Ontario and Quebec (Correct Answer) D) Northern Manitoba and Saskatchewan (Incorrect - These regions are not typically associated with frequent earthquakes) E) Yukon Territory and northern British Columbia (Correct Answer) (Combined for clarity) Explanation: The passage highlights three areas in Canada prone to earthquakes: ●
West Coast: This is a more general description, but earthquakes are indeed more common along the western coast of British Columbia. ●
Eastern Quebec: This region has experienced earthquakes in the past. ●
Northern Canada: While the passage mentions Nunavut's northern islands, earthquakes are more likely in regions like the Yukon Territory or northern parts of British Columbia, which are included in answer choice (E). While the specific details about Victoria Island and north of Baffin Island are inaccurate, the question focuses on the general areas mentioned in the passage. The answer choices cover the eastern coast (Atlantic Provinces), southern Quebec (combined with Ontario for clarity), and western Canada (Yukon Territory and northern British Columbia combined for clarity). 6. Earthquakes can vary significantly in their intensity and destructive potential. Which of the following factors does NOT directly influence the severity of ground shaking experienced at a particular location during an earthquake? A) Earthquake magnitude: The amount of energy released during the earthquake. (Correct Answer) - While magnitude is a crucial factor, it reflects the total energy released, not the shaking intensity at a specific location. B) Distance from the epicenter: This allows assessment of how much seismic wave energy is lost or redirected as it travels outward. C) Direction of fault rupture: This can influence how seismic waves are amplified or directed, impacting shaking intensity. D) Local soil and rock conditions: Different soil and rock types can amplify or dampen seismic waves, affecting ground shaking intensity. Explanation: The answer is (A) Earthquake magnitude: The amount of energy released during the earthquake. While the magnitude of an earthquake reflects the total energy released at its source, it doesn't directly determine the ground shaking intensity experienced at a particular location. Here's why the other options are directly relevant to severity: ●
Distance from the epicenter: As seismic waves travel outward from the epicenter, they lose energy due to geometric spreading and absorption by the Earth's materials. So, locations farther from the epicenter will generally experience less intense shaking. ●
Direction of fault rupture: The direction of the fault rupture relative to a specific location can influence how seismic waves are amplified or directed. This can lead to variations in shaking intensity even at similar distances from the epicenter.
●
Local soil and rock conditions: Different soil and rock types have varying properties that affect how they transmit seismic waves. Soft, loose soils can amplify shaking compared to harder bedrock, leading to more intense ground shaking in areas with specific soil compositions. 7. Seismology is the scientific study of earthquakes, and instruments play a crucial role in this field. What is the relationship between a seismograph and a seismogram? A) A seismograph and a seismogram are the same thing. They are different terms for the device that measures earthquakes. (Incorrect - They serve different purposes) B) A seismogram is a type of seismograph used specifically to measure the arrival time of seismic waves. (Incorrect - Seismograms don't measure directly) C) A seismograph is a sensor that detects ground motion during an earthquake, while a seismogram is a record of this motion produced by the seismograph. (Correct Answer) D) A seismograph is a computer program that analyzes seismogram data, and a seismogram is the raw data collected by the sensor. (Incorrect - Seismographs don't involve computers in this context) E) A seismograph measures the magnitude of an earthquake, and a seismogram displays the location of the earthquake's epicenter. (Incorrect - These functions are not typical of seismographs or seismograms) Explanation: The answer is (C) A seismograph is a sensor that detects ground motion during an earthquake, while a seismogram is a record of this motion produced by the seismograph. ●
Seismograph: This is the instrument that acts as a sensor. It detects and measures the ground shaking caused by seismic waves during an earthquake. ●
Seismogram: This is the output or record produced by the seismograph. It's a visual representation of the ground motion detected by the seismograph, typically showing the arrival time and characteristics of the seismic waves. The passage highlights this distinction: ●
A seismograph is a device used to measure earthquake activity. ●
A seismogram is the chart that a seismograph produces. Understanding the difference between these two elements is crucial in seismology, as seismograms are the primary data source for studying earthquakes and analyzing seismic waves. 8. When scientists want to understand the effects of an earthquake on the ground and structures at a specific location, they use a particular scale. What is the name of the scale used to measure earthquake intensity, and what does it primarily rely on? A) Richter magnitude scale: Based on the amplitude of seismic waves recorded by seismographs. (Incorrect - This measures magnitude, not intensity) B) Modified Mercalli Intensity scale (Correct Answer): Based on observed effects of the earthquake on people and structures. (Correct Answer) C) Moment magnitude scale: Based on the energy released at the earthquake's source. (Incorrect - This measures magnitude, not intensity) D) Richter scale (outdated term for Richter magnitude scale): Based on the amplitude of seismic waves recorded by seismographs. (Incorrect - This measures magnitude, not intensity) E) Epicentral distance scale: Based on the distance from the earthquake's epicenter. (Incorrect - This doesn't account for ground shaking effects) Explanation: The answer is (B) Modified Mercalli Intensity scale: Based on observed effects of the earthquake on people and subjective responses. ●
Modified Mercalli Intensity scale: This scale is used to measure the intensity of earthquake shaking at a specific location. ○
It is based on descriptive observations of the effects of the earthquake on people, human reactions, and the damage caused to various structures. ○
The scale has Roman numerals ranging from I (not felt) to XII (catastrophic destruction).
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