Podcast
Questions and Answers
How is the Modified Mercalli Intensity Scale primarily characterized?
How is the Modified Mercalli Intensity Scale primarily characterized?
Which term describes the block that is located below a fault plane?
Which term describes the block that is located below a fault plane?
What distinguishes a normal fault from a thrust fault?
What distinguishes a normal fault from a thrust fault?
Which statement is true regarding strike slip faults?
Which statement is true regarding strike slip faults?
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Which feature is NOT mentioned as evidence of strike slip faults?
Which feature is NOT mentioned as evidence of strike slip faults?
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What is the primary mechanism behind dip-slip faulting?
What is the primary mechanism behind dip-slip faulting?
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Why are certain faults considered more dangerous despite no visible cracks appearing on the surface?
Why are certain faults considered more dangerous despite no visible cracks appearing on the surface?
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What type of fault is characterized by vertical displacements where the hanging wall moves down relative to the footwall?
What type of fault is characterized by vertical displacements where the hanging wall moves down relative to the footwall?
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What is the primary effect of tsunamis on coastal landscapes?
What is the primary effect of tsunamis on coastal landscapes?
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Which method is NOT part of tsunami detection and warning systems?
Which method is NOT part of tsunami detection and warning systems?
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What should individuals NOT do when they feel a strong earthquake in coastal areas?
What should individuals NOT do when they feel a strong earthquake in coastal areas?
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Which of the following is considered a secondary effect of tsunamis?
Which of the following is considered a secondary effect of tsunamis?
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What is a key strategy for minimizing the tsunami hazard?
What is a key strategy for minimizing the tsunami hazard?
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Which stage in the earthquake cycle comes after the accumulation of elastic strain?
Which stage in the earthquake cycle comes after the accumulation of elastic strain?
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What primarily causes damage to buildings during an earthquake?
What primarily causes damage to buildings during an earthquake?
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Which of the following is NOT considered a secondary effect of earthquakes?
Which of the following is NOT considered a secondary effect of earthquakes?
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What phenomenon occurs when the vibrational frequencies of the ground match those of a building?
What phenomenon occurs when the vibrational frequencies of the ground match those of a building?
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In which geographic region do approximately 80% of all earthquakes occur?
In which geographic region do approximately 80% of all earthquakes occur?
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Which of the following factors does NOT influence the intensity of shaking from an earthquake?
Which of the following factors does NOT influence the intensity of shaking from an earthquake?
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What is the main cause of cracks in the surface during an earthquake?
What is the main cause of cracks in the surface during an earthquake?
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Which of the following materials typically allows seismic waves to travel more slowly?
Which of the following materials typically allows seismic waves to travel more slowly?
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What is the primary distinction between predicting and forecasting earthquakes?
What is the primary distinction between predicting and forecasting earthquakes?
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Which method is least likely to provide reliable earthquake predictions?
Which method is least likely to provide reliable earthquake predictions?
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Which tectonic plate boundary is associated with causing shallow earthquakes?
Which tectonic plate boundary is associated with causing shallow earthquakes?
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What is a key component of community preparedness for earthquakes?
What is a key component of community preparedness for earthquakes?
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What role do seismic risk maps play in earthquake preparedness?
What role do seismic risk maps play in earthquake preparedness?
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Which of the following is NOT a characteristic of foreshocks?
Which of the following is NOT a characteristic of foreshocks?
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What is a limitation of animal behavior as a predictor for earthquakes?
What is a limitation of animal behavior as a predictor for earthquakes?
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What is necessary for buildings to effectively withstand earthquake vibrations?
What is necessary for buildings to effectively withstand earthquake vibrations?
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What characterizes an active fault?
What characterizes an active fault?
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Which type of seismic wave is the fastest?
Which type of seismic wave is the fastest?
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What is a characteristic of S waves?
What is a characteristic of S waves?
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What is required to determine the exact location of an earthquake's epicenter?
What is required to determine the exact location of an earthquake's epicenter?
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Which statement is true regarding blind faults?
Which statement is true regarding blind faults?
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What type of wave causes horizontal shaking?
What type of wave causes horizontal shaking?
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Which of the following statements about seismic waves is true?
Which of the following statements about seismic waves is true?
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What phenomenon occurs when movement along a fault is gradual and not felt as an earthquake?
What phenomenon occurs when movement along a fault is gradual and not felt as an earthquake?
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Study Notes
Earthquake Energy Release
- Energy released by a magnitude 3 earthquake is 32 times greater than that of a magnitude 2 earthquake.
Earthquake Intensity
- Measured by the Modified Mercalli Intensity Scale, which is qualitative, assessing structural damage and human perception.
- Intensity maps illustrate regions of severe damage and shaking.
- Internet data collection enhances the creation of shake maps using seismographic data.
Fault Movements
- Earthquakes occur along faults, weaknesses in the Earth's crust where rocks break and displace.
- Types of faults include:
- Strike-slip faults: Horizontal displacements (e.g., San Andreas Fault) evidenced by surface cracks.
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Dip-slip faults:
- Thrust or reverse faults: Hanging wall moves up relative to footwall.
- Normal faults: Hanging wall moves down relative to footwall, occurring due to crustal stretching.
- Blind faults: Do not reach the surface, complicating earthquake risk assessment, often formed by mountain-building processes.
Fault Activity
- Active faults: Movement in the last 11,600 years.
- Potentially active faults: Movement in the past 2.6 million years.
- Inactive faults: No movement in the last 2.6 million years.
- Tectonic creep: Gradual fault movement that may not produce felt earthquakes, potentially damaging infrastructure.
Seismic Waves
- Seismic waves: Produced by sudden rock displacement; travel through or along Earth's surface.
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Types of body waves:
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P-waves (Primary):
- First to appear on seismographs, faster than S-waves.
- Can traverse solids, liquids, and gases.
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S-waves (Secondary):
- Appear second on seismographs, slower with an up-and-down motion.
- Can only travel through solids.
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P-waves (Primary):
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Surface waves:
- Travel along the Earth's surface, causing horizontal and vertical motion.
- Responsible for significant damage near the epicenter, includes:
- Love waves: Cause horizontal shaking.
- Rayleigh waves: Produce rolling, elliptical motion.
Epicenter Location
- At least three seismic stations needed to identify the epicenter using triangulation.
- Focal depth affects shaking intensity due to wave attenuation.
Earthquake Cycle
- Consists of an inactive period with stress accumulation, followed by small earthquakes and potential foreshocks before a mainshock.
- Major stages include periods of inactivity, buildup of elastic strain, occurrence of foreshocks, and the main earthquake event with subsequent aftershocks.
Geographic Regions
- Approximately 80% of earthquakes occur within the circum-Pacific belt.
Effects of Earthquakes
- Primary effects: Shaking and surface rupture; ground rupture induces surface cracks, while shaking damages structures based on factors like depth and direction of the epicenter.
- Secondary effects: Include liquefaction, land level changes, landslides, fires, tsunamis, and diseases.
Earthquake Forecasting
- Earthquakes cannot be predicted with certainty; only forecasted.
- Indicators for forecasting include patterns of past earthquakes, surface deformations, and seismic gaps.
Animal Behavior
- Historical beliefs exist that animals predict earthquakes through changes in behavior, though evidence remains inconclusive.
Minimizing Earthquake Hazards
- Strategies include:
- Use of seismic risk maps to assess future earthquake likelihood.
- Community preparation through education, retrofitting buildings, and locating critical facilities in safe areas.
- Nationwide economic impact, with $250 billion noted as the costliest natural disaster.
Tsunami Effects
- Primary effects include flooding and erosion, impacting coastal areas and causing deaths.
- Secondary effects involve fires, water contamination, and disease spread.
Tsunami Hazard Minimization
- Detection systems monitor earthquake zones with technologies like seismographs, tidal gauges, and buoy sensors.
- Alerts are communicated through satellite for timely public warnings.
Personal Safety During Tsunamis
- Immediate actions include evacuating low-lying areas upon strong earthquakes or ocean recession.
- Awareness of wave timing is essential, as intervals between waves can be significant.
- Preparedness includes education and community strategies to mitigate tsunami risks.
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Description
This quiz covers key concepts related to earthquakes, including the energy released during seismic events, how intensity is measured using the Modified Mercalli Scale, and the different types of fault movements. Test your understanding of these crucial geological processes and learn more about earthquake risks and assessments.
