Earth science - 19
Most earthquakes occur near the _________ of tectonic plates.
Boundaries
Are rocks near Earth's surface generally brittle or plastic? Rocks at great depths?
Brittle; plastic
What can occur on a steep slope during an earthquake?
Buildings collapse
How is the height of a building related to damage caused during an earthquake?
Buildings that have the same period of vibrations as earthquakes do are destroyed.
What can happen during earthquakes in areas where the ground contains fluid-saturated sand?
Causes trees and houses to fall over or to sink into the ground or underground pipes and tanks to rise to the surface.
Nearly 80 percent of earthquakes occur in the seismic belt known as the _____________.
Circum-pacific belt
Which occurs at a lower stress value, plastic deformation or elastic deformation?
Elastic deformation
Maximum earthquake intensity is usually found at the earthquake's
Epicenter
On seismograms, seismic waves recorded from more distant facilities are closer together than those recorded from facilities close to the epicenter
False
S-Waves do not travel through Earth's mantle
False
S-waves do not enter the core because they cannot travel through solids.
False
Surface waves are the first to arrive at a seismic station
False
Fracture along which movement occurs
Fault
Fault surface along which movement takes place
Fault plane
The moment magnitude scale takes into account the size of an earthquake's
Fault rupture
One factor that determines the strength of an earthquake is the depth of its
Focus
All seismometers include a ________ that is anchored to the ground and vibrates during an earthquake.
Frame
Upon what two factors is the probability of earthquake occurrences based?
History of earthquakes and the rate at which stress builds up in the rocks
The modified-Mercalli scale ranges from
I-XII
The amount of damage done to structures by an earthquake is the earthquake's
Intensity
As the distance from a quake's epicenter increases
Intensity decreases
How would a rubber structure beneath a building prevent if from being damaged?
It would absorb the vibrations
The modified-Mercalli scale measure an earthquake's
Itensity
The Richter scale is a numerical scale used to describe an earthquake's
Magnitude
The amount of energy released by an earthquake is measured by its
Magnitude
All seismometers include a _______________ suspended from a wire or spring.
Mass
About 15 percent of all earthquakes occur in the _________________, which stretches across Europe and Asia.
Mediterranean-Asian belt
Is an area that has already experienced past earthquakes more or less likely to experience a future earthquake than an area that has never had an earthquake?
More likely, because the area already had one
Can the location of an epicenter be determined from the distance between one seismic station and the epicenter? If not, what information is needed?
No; data from three or more seismic stations are needed to find the location of the epicenter
Fracture caused by horizontal tension
Normal fault
Most other earthquakes occur on the crests of _________.
Ocean ridges
Squeezes and pulls rock in the same direction as the wave travels
P-Wave
To determine an epicentral distance, scientists consider the arrival times of what wave types?
P-waves and S-waves
Fracture that forms as a result of horizontal compression
Reverse fault
Causes rock to move at right angles to the direction in which the wave travels
S-Wave
Can pass through Earth's interior
S-Wave, P-Wave
Famous California strike-slip fault
San Andreas
Most earthquakes occur in narrow __________ that lie between large regions with little or no seismic activity.
Seismic belts
Each whole-number increase on the Richter scale corresponds to a 32-fold increase in
Seismic energy
The time an earthquake occurred can be estimated from the
Seismic wave size
A paper or computer record of earthquake vibrations is called a ________________.
Seismogram
A _____________ is an instrument that records earthquake vibrations.
Seismometer
The focus of a catastrophic earthquake with high intensity values is almost always
Shallow
What is a seismic gap?
Station located along faults that are known to be active but which haven't experienced significant earthquakes for a long period of time
What is compression?
Stress that decreases the volume of a material
What is tension?
Stress that pulls a material apart
Causes rock to move both up and down and from side to side
Surface wave
Travels only along Earth's surface
Surface wave
Earthquake intensity depends primarily on the height of
Surface waves
Seismic activity is seismic belts is a result of movements among Earth's __________.
Tectonic
What is strain?
The deformation of minerals in response to stress
On the stress-strain curve, what part of the curve represents the elastic deformation of a material? What part represents plastic deformation?
The lower straight segment of the curve represents elastic deformation, and the upper curved segment represents plastic deformation.
What happens when stress exceeds the strength of a material?
The material goes ductile deformation (material fails)
What is stress?
The total force acting on crustal rocks per unit of area
What takes place during the process called "pancaking"?
The walls on the ground floor failed and caused the upper floors to collapse as they hit the ground
How are seismic waves changed as they pass through soft soils?
They are amplified
P-waves are bent when they strike the core
True
P-waves travel through Earth's mantle
True
Seismic waves change speed and direction when they encounter different materials.
True
Seismologists have reasoned that Earth's outer core must be liquid based on the disappearance of S-waves.
True
Studies of how waves reflect deep inside Earth show the Earth's inner core is solid.
True
The P-wave shadow zone does not receive direct P-waves.
True
What kinds of structures suffer the most severe damage from an earthquake?
Unreinforced buildings made with concrete
Fracture caused by horizontal shear
strike-slip fault