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exam 2 highlights
chap 5
Question | Answer |
---|---|
What are the vibrations caused by earthquakes? | seismic waves |
Several types of waves are all produced at the | same time |
How can the location of an earthquake be determined? | from data recorded by seismographs |
How can the magnitude (size) of an earthquake be determined? | from data on a seismogram |
The vibrations that travel through rocks are recorded on instruments called | seismographs |
After an earthquake, what waves arrive at the seismograph stations first? | body waves |
Why do body waves arrive first to the seismograph stations? | they take a more direct route and they travel at faster velocities than surface waves |
When is there less of a difference between the arrival times for P and S waves? | when the recording stations are closer to the focus |
When seismograph stations are a greater distance away from the focus, | there is a greater arrival time between the P and S waves |
What waves travel along earths surface? | surface waves |
What waves travel through the earths interior? | body waves |
What are the two types of surface waves? | rayleigh and love waves |
Rayleigh waves | produce vertical motions of the land surface |
Love waves | move sideways but not vertically |
Surface waves are classified on the basis of their | motion |
What are the two types of body waves? | P and S waves |
What body wave has the highest-velocity? | Primary or P waves |
Why are P-waves the highest-velocity waves? | they are first waves to arrive at a distant seismograph |
Where can P-waves travel at faster speeds? | in the mantle and core |
How fast do P-waves travel? | 4-6 km per second, 2.5-4 miles per second |
How fast do S-waves travel? | 3 to 4 km per second, 2-2.5 miles per second |
Which body wave cant pass through liquids? | S-waves |
Fastest seismic waves are | P waves are fastest |
What are the intermediate in velocity waves? | S-waves are intermediate |
What waves are the slowest? | surface waves are the slowest |
What waves are similar to the passage of a vibration through a slinky? | P-waves are like a slinky, the vibration occurs in the same direction that the wave travels |
Which wave is analogous to a vibration moving along a rope? | S-wave motion, the vibration occurs perpendicular to the direction in which the wave travels |
How do you determine earthquake location? | the time interval between the arrival of P and S waves |
The time interval between the arrival of P and S waves increases with | increasing distance from the earthquake focus |
How do you determine the distance to the epicenter? | The time interval is compared with the estimated rate curves (red and blue lines) |
What do the circles plotted at each station reflect? | the distance from the epicenter to that station |
The epicenter is the intersection of the | three circles |
What does the earthquake magnitude scale measure? | the shaking associated with an earthquake, using information recorded on a seismogram |
How is earthquake intensity defined | by the amount of damage resulting from an earthquake and by descriptions of what humans experienced during the event |
What is the shaking and energy released from different earthquakes compared by using? | earthquake magnitudes |
What is earthquake intensity? | a measure of the effects of earthquakes on people and buildings |
How is the earthquake magnitude measured? | on a logarithmic scale in which each division represents a 10-fold increase in the ground motion |
Earthquake magnitude scale does not have a | maximum |
because earthquake magnitude is logarithmic, a magnitude 5 earthquake has ____times as much ground motion as a magnitude 4 earthquake? | 10 times |
How are earthquakes classified? | small to great, depending on their magnitude |
What is the correlation that scientists found between fault length and earthquake magnitude? | the longer the fault rupture, the bigger the earthquake |
What is a damage-based scale that was developed to compare different earthquakes? | Modified Mercalli Scale |
What does the Modified Mercalli Scale use? | both damage to structures and the experiences of people to define a measurement system |
How is the Modified Mercalli scale ranked? | earthquake intensity from I-XII (1-12) using roman numerals |
What types of destruction can earthquakes cause? | violent ground shaking, aftershocks, landslides, fault ruptures, liquefaction, and tsunami |
Scientists express ground shaking as a proportion of the | acceleration due to gravity (g) |
The double-deck Cypress freeway was constructed on what two underlying materials? | sand and gravel, soft mud |
During the 6.7 magnitude Loma Prieta earthquake, the section of the freeway constructed on the weaker mud experienced | much more skaing and collapsed |
Seismograms of the three different materials near the Cypress freeway illustrate that | shaking was lease for bedrock and greatest for mud |
Once an earthquake occurs (the main shock), it is followed by | aftershocks |
The aftershocks are earthquakes that occur | on or nearby faults for months or even years after the main shocks |
the larger the main earthquake, the | more plentiful, and larger the aftershocks are |
Earthquakes are often associated with mountains formed along | convergent plate boundaries |
How do landslides occur? | if slopes are steep and the rocks, soils, and materials forming the slope are not stable |
How do large sections of earths surface change elevations? | when a fault undergoes vertical motion |
What occurs when shaking of the ground causes compaction of the sediment. | liquefaction |
When liquefaction occurs, it increases water pressure resulting in | water-saturated materials being violently ejected at the surface |
What is created by movement that can displace large volumes of ocean water? | tsunamis |
step 1 of a tsunami | friction along a sediment of the plate boundary locks the overriding plate and the subducting plate |
step 2 of a tsunami | the shape of the overriding plate is distorted as it is pulled toward the subduction zone as the lower plate continues to descend. This can continue for hundreds of years |
step 3 of a tsunami | the stress finally breaks the locked portion of the fault, resulting in an earthquake. When the plate snaps up, it causes the seafloor to move upward pushing the water out of the way and forming a tsunami |
step 4 of a tsunami | the tsunami moves outward from the source area at speeds of hundreds of kilometers per hour |