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78 Cards in this Set
- Front
- Back
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Most quakes occur where?
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Along plate boundaries
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What is pancaking?
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Pancaking occurs when overlying floors pile up on lower floors of buildings
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What does the Richter Scale measure?
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The energy of seismic waves, which is the amplitude of an earthquake.
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What does the moment magnitude scale measure?
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The Moment magnitude scale measures energy of an earthquake
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What does the Moment magnitude scale take into consideration when determining the energy of an earthquake?
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The size of the fault rupture
The amount of movement along the fault and The rock's stiffness |
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The amount of energy released by an earthquake is measured by its what?
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Magnitude
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The Richter scale is a numerical scale used to describe an earthquake's what?
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Amplitude
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Each whole number increase on the Richter scale corresponds to a 32-fold increase in what?
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Seismic Energy
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The moment magnitude scale takes into account the size of an earthquake's what?
Epicenter Fault rupture Probability or Intensity |
Fault Rupture
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The amount of damage done to structures by an earthquake is the earthquake's what?
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Intensity
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The time an earthquake occurred can be estimated from the what?
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Seismic Wave Size
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The modified Mercalli Scale measures and earthquake's what?
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intensity
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The modified Mercalli scale ranges from what to what?
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1 to 12
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Earthquake intensity depends primarily on the height of the what?
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surface waves.
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As the distance from a quake's epicenter increases, does the intensity increase, does the intensity decrease, does the magnitude increase, or does the focus decrease?
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The intensity decreases.
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Maximum earthquake intensity is usually found at the earthquake's what?
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Epicenter
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One factor that determines the strength of the earthquake is the depth of its what?
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Focus
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The focus of a catastrophic earthquake with high intensity values is almost always what?
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Shallow
(Close to the surface) |
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To determine an epicentral distance, scientists consider the arrival times of what wave types?
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P waves and S waves
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Can the location of an epicenter be determined from the distance between one seismic station and the epicenter? If not, what info is needed?
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No, you need info from three seismic stations in all. You would need two more distances.
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Most earthquakes occur in narrow _________ _______s that lie between large regions with little or no seismic activity.
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seismic belts
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Seismic activity in seismic belts is a result of movements among Earth's _______ _______s.
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tectonic plates.
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Most earthquakes occur near the _________ of tectonic plates.
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boundaries.
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Nearly 80 percent of earthquakes occur in the sismic belt known as the _________ belt.
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Circum-Pacific.
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About 15 percent of earthquakes occur in the ___________ belt.
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Mediterranean-Asian Belt
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the remaining five percent of earthquakes occur on the crests of _______ ________s.
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Ocean ridges.
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A ___________ is an instrument that records earthquake vibrations.
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seismometer
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All seismometers include a ____ suspended from a wire or spring.
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mass
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A paper or computer record of earthquake vibrations is called a ________.
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Seismogram
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All seismometers include a ______ that is anchored to the ground and vibrates during an earthquake.
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frame.
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T or F
Seismic waves change speed and direction when they encounter different materials. |
true
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T or F
P waves travel through earth's mantle? |
true.
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T or F
S waves do not travel through Earth's mantle. |
False. They do.
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T or F
Surface waves are the first to arrive at a seismic facility. |
False, they are the last.
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T or F
P waves are bent when they strike the core. |
True
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T or F
On seismograms, seismic waves recorded from more distant facilities are closer together than those recorded from facilities close to the epicenter. |
false
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T or F
S waves do not enter the core because they cannot travel through solids |
False, they do not enter the core because they cannot travel through liquids.
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T or F
Seismologists have reasoned that Earth's outer core must be liquid based on the disappearance of s waves. |
true
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T or F
Studies of how waves reflect deep inside Earth show that Earth's inner core is solid. |
True
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T or F
The p wave shadow zone does not receive direct P waves. |
true
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What is a fracture that forms as a result of horizontal compression?
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Reverse fault
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What is a fracture caused by horizontal shear?
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A strike slip fault
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Famous California strike slip fault
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San-Andreas Fault
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what is a Fracture caused by horizontal tension?
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Normal Fault
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What is a fracture along which movement occurs?
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Fault
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What is a fault surface along which movement takes place?
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a fault plane
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What type of seismic waves causes rock to move both up and down and side to side?
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Surface waves
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What type of seismic waves causes rock to move at right angles to the direction in which the wave travels?
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S waves
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What type of seismic wave squeezes and pulls rock in the same direction as the wave travels?
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P waves
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Which seismic waves can pass through Earth's interior?
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P and S waves
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Which seismic waves travels only along earth's surface?
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surface waves.
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What is stress?
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Total force acting on crustal rocks per unit of area
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what is strain
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Deformation of materials in response to stress
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What is compression?
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Stress that decreases the volume of a material
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What is tension?
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Stress that pulls a material apart
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What happens when stress exceeds the strength of a material?
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The material fails, breaks, or fractures.
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On the stress strain curve, what part of the curve represents the elastic deformation of a material? What part represents plastic deformation?
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The line with the largest slope represents the elastic deformation of a material and the line that has the smaller slope represents plastic deformation
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Which occurs at a lower stress value, plastic deformation or elastic deformaion?
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elastic
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Are rocks near Earth's surface generally brittle or plastic? Rocks at great depths?
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Near Earth's surface- brittle
Deeper- Plastic |
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What kinds of structures suffer the most severe damage from an earthquake?
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Unreinforced buildings made of brittle building materials like concrete.
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How would a rubber structure beneath a building prevent it from being damaged?
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The rubber is more elastic than other materials. It absorbs vibrations
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What takes place during the process called pancaking?
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During pancaking, supporting walls of the ground beneath shakes. Upper floors fall to collapse as they hit the ground or lower floors.
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How is the height of a building related to damage caused during an earthquake?
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Ground vibrations are too rapid sometimes to affect taller buildings . Buildings whose vibrations match the eqs vibration experience the most damage.
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What can happen during eqs in areas where the ground contains fluid saturated sand?
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seismic vibrations can cause soil liquefaction, which can generate landslides even in areas of low relief and trees and houses can fall over. It can also act as a quick sand where buildings can sink into Earth.
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How are seismic waves changed as they pass through soft soils?
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Seismic waves are amplified in some soft materials.
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What can occur on a steep slope during an earthquake?
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On steep slopes, massive landslides can occur.
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Is an area that has experienced past earthquakes more or less likely to experience a future earthquake than an area that has never had one?
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more likely
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Upon what two factors is the probability of earthquake occurrence based?
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History of earthquakes and knowing where and how quickly strain accumulates.
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What is a seismic gap?
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Seismic gaps are sections located along faults that are known to be active, but have not experienced significant eqs for a long time.
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Explain why faults form.
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When forces acting on rock exceed the rock's strength
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At what type of plate boundary do reverse faults occur? Normal faults?
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Reverse- convergent
Normal- divergent |
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What causes an earthquake?
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The movement of earth's crust produced by plate tectonics.
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Explain the relationship between a seismometer and a seismogram.
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Seismometers detect vibrations caused by seismic waves and seismograms record them.
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What damage would be caused by an earthquake with a modified mercalli rating of 9?
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Great general damage, buildings shift off of foundations, ground cracks, underground pipes break.
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Explain how the arrival of p waves can determine the exact time of an earthquake.
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The time of occurrence can be determined by the time difference between the p and s waves at a seismic station.
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Explain how triangulation is the best method of determining an epicenter of an earthquake.
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Triangulation is best because it gives a definite direction from three or more locations.
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what two factores influence deformation?
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pressure and temperature.
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What are body waves?
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Body waves can travel through the earth. surface waves cannot. p and s waves are body waves.
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