Podcast
Questions and Answers
What is formed when the rupture of an earthquake reaches Earth's surface?
What is formed when the rupture of an earthquake reaches Earth's surface?
- Strike-slip fault
- Fault scarp (correct)
- Normal fault
- Shear zone
Which of the following best describes the movement associated with a normal fault?
Which of the following best describes the movement associated with a normal fault?
- Horizontal and vertical movement equally balanced
- Vertical movement primarily downward (correct)
- Horizontal movement with no vertical displacement
- Vertical movement primarily upward
Which factor influences the stopping point of an earthquake rupture?
Which factor influences the stopping point of an earthquake rupture?
- Temperature of the fault surface
- Remaining stress versus friction along the fault (correct)
- Magnitude of the earthquake
- Orientation of the fault line
What happens to fault scarps over time?
What happens to fault scarps over time?
What is associated with the East California Shear Zone?
What is associated with the East California Shear Zone?
During the Borah Peak earthquake, what type of movement primarily caused the land surface to rupture?
During the Borah Peak earthquake, what type of movement primarily caused the land surface to rupture?
Which statement is false regarding the rupture process of an earthquake?
Which statement is false regarding the rupture process of an earthquake?
What characteristic is typical of fault scarps immediately after an earthquake?
What characteristic is typical of fault scarps immediately after an earthquake?
What happens when the stress along a fault exceeds its ability to resist?
What happens when the stress along a fault exceeds its ability to resist?
What does the orange dot on the stress-versus-time graph represent?
What does the orange dot on the stress-versus-time graph represent?
What type of behavior is characterized by rocks sticking and then slipping?
What type of behavior is characterized by rocks sticking and then slipping?
After an earthquake, how do rocks adjacent to the fault typically respond?
After an earthquake, how do rocks adjacent to the fault typically respond?
From where does an earthquake rupture typically begin on a fault?
From where does an earthquake rupture typically begin on a fault?
What generally occurs during the expansion of an earthquake rupture?
What generally occurs during the expansion of an earthquake rupture?
What does the black dot at the end of the stress-versus-time line signify?
What does the black dot at the end of the stress-versus-time line signify?
What is the primary characteristic of a fault during the stick-slip behavior phenomenon?
What is the primary characteristic of a fault during the stick-slip behavior phenomenon?
What type of seismic wave is characterized by its ability to travel through both solids and liquids?
What type of seismic wave is characterized by its ability to travel through both solids and liquids?
Which seismic wave is defined by its motion being perpendicular to the direction of travel?
Which seismic wave is defined by its motion being perpendicular to the direction of travel?
What is the primary reason S-waves do not travel through the outer core of the Earth?
What is the primary reason S-waves do not travel through the outer core of the Earth?
Which of the following waves is not categorized as a surface wave?
Which of the following waves is not categorized as a surface wave?
What type of wave moves the Earth’s surface in an elliptical path?
What type of wave moves the Earth’s surface in an elliptical path?
Which instrument is used to record seismic waves?
Which instrument is used to record seismic waves?
What type of surface wave moves horizontally and causes shuffling side to side?
What type of surface wave moves horizontally and causes shuffling side to side?
What is the primary effect of surface waves during an earthquake?
What is the primary effect of surface waves during an earthquake?
What correction factor is applied to the mean peak acceleration for soft soil?
What correction factor is applied to the mean peak acceleration for soft soil?
Which type of earthquake hazard involves the deformation of the ground at a fault's surface?
Which type of earthquake hazard involves the deformation of the ground at a fault's surface?
What is a primary consequence of ground shaking during an earthquake?
What is a primary consequence of ground shaking during an earthquake?
What effect is associated with liquefaction during an earthquake?
What effect is associated with liquefaction during an earthquake?
Which earthquake hazard can cause coastal erosion as a primary effect?
Which earthquake hazard can cause coastal erosion as a primary effect?
What phenomenon commonly triggers earthquake-induced landslides?
What phenomenon commonly triggers earthquake-induced landslides?
Which of the following effects is NOT associated with ground shaking?
Which of the following effects is NOT associated with ground shaking?
What does ground rupture primarily cause?
What does ground rupture primarily cause?
What was the estimated magnitude of the Charleston earthquake in 1886?
What was the estimated magnitude of the Charleston earthquake in 1886?
What is one factor that affects how seismic waves travel through materials?
What is one factor that affects how seismic waves travel through materials?
What happens to seismic waves when they encounter a boundary between different materials?
What happens to seismic waves when they encounter a boundary between different materials?
What is the term for the process by which seismic waves change direction as they pass through different materials?
What is the term for the process by which seismic waves change direction as they pass through different materials?
If a seismic wave passes into a material that slows it down, what is the expected behavior of the wave?
If a seismic wave passes into a material that slows it down, what is the expected behavior of the wave?
What is the outcome when a seismic ray moves from a slow material to a faster one?
What is the outcome when a seismic ray moves from a slow material to a faster one?
Which of the following describes the primary reason for the occurrence of seismic rays diverging outward from the source?
Which of the following describes the primary reason for the occurrence of seismic rays diverging outward from the source?
What was the significant impact of the Charleston earthquake in 1886?
What was the significant impact of the Charleston earthquake in 1886?
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Study Notes
Slip and Earthquake
- Faults slip when stress exceeds their resistance, causing rapid movement of rocks.
- Earthquakes occur at specific points where friction is insufficient to hold the fault in place.
Post-Slip Dynamics
- After slip, rocks near the fault relax and return to their original shape, but the slip is permanent.
- Stick-slip behavior involves elastic strain before earthquakes and permanent deformation after.
Earthquake Rupture Growth
- Earthquake ruptures initiate at a hypocenter and gradually expand along preexisting fault lines.
- Most slip occurs on the fault surface, which is weaker than surrounding intact rock.
Fault Scarp Formation
- Rupture expansion may reach the Earth's surface, creating a fault scarp.
- Ruptures grow outward, but may expand more in one direction than another.
Visuals of Earthquake Rupture
- Earthquake-induced fault scarps can cut through solid rock, as seen in granite formations.
- Historical examples include the Borah Peak earthquake (1983) and the Hebgen Lake earthquake (1959), both creating significant fault scarps.
Erosion of Scarps
- Scarps become less prominent over time due to erosion and sediment accumulation that shape the landscape.
Buildup and Release of Stress
- Stress cycles lead to eventual earthquake events when stress overcomes friction along faults.
Seismic Wave Types
- P-waves (Primary waves): Fast, can travel through solids and liquids; compressibility allows movement.
- S-waves (Secondary waves): Slower, shear rocks side to side; cannot move through liquids, indicating molten regions within Earth.
Surface Waves
- Include Rayleigh waves (vertical movement similar to ocean waves) and Love waves (horizontal side-to-side motion); both are destructive during earthquakes.
Seismometer Functionality
- Instruments that detect seismic activity, recording data from numerous locations for analysis.
Historical North American Earthquakes
- Charleston Earthquake (1886): Magnitude 7.3, caused fatalities and damage; origin and tectonic cause still under debate.
Seismic Wave Propagation
- Seismic waves radiate outward and are influenced by the Earth's material properties, which can alter their path and speed through reflection and refraction.
Seismic Wave Refraction
- Waves refract away from boundaries where they slow down or speed up, changing angles based on material transitions.
Geo-hazard Assessment Factors
- Correction factors for peak acceleration based on foundation type:
- Rock: 0.6, Hard soil: 0.87, Medium soil: 1.07, Soft soil: 1.39.
Types of Earthquake Hazards
- Ground Rupture: Visible deformation marking fault intersections, leading to fissures and ground displacement.
- Ground Shaking: Vibrations cause structural damage, liquefaction, and landslides.
- Liquefaction: Sediments behave like liquids, potentially causing structures to sink or tilt.
- Earthquake-induced Landslide: Movement of debris triggered by shaking, leading to erosion and road obstructions.
- Tsunami: Waves generated by underwater earthquakes causing coastal flooding and destruction.
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