Earthquakes - Science
What is a seismic gap?
A section of an active fault that hasn't experienced a significant earthquake for a long time
T or F- S-waves do not enter the core because they cannot travel through solids
S-waves do not enter the core because they cannot travel through liquids They can travel through solids, but not liquids
Famous California Strike-Slip fault
San Andreas
Causes rock to move at right angles to the direction in which the wave travels
Secondary Waves
A paper or computer record of earthquake vibrations is called a _______
Seismogram
A _____ is a intrument that records earthquake vibrations
Seismometer
What is tension?
Stress that pulls a material apart
Causes rock to move both up and down and from side to side
Surface waves
Travels only along earths surface
Surface waves
Seismic activity in seismic belts is a result of movements among Earth's _____ _____
Techtonic Plates
Which occurs at a lower stress value, ductile deformation or elastic deformation?
elastic deformation
Maximum earthquake intensity is usually found at the earthquake's
epicenter
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 is the height of a building related to damage caused during an earthquake?
Builings that sway with the same period of vibration as the earthquake waves sway violently and are destroyed.
Nearly 80 percent of earthquakes occur in the seismic belt known as the _____________ ______
Circum-Pacific Belt
Upon what two factors is the probability of earthquake occurance based?
Earthquake history in a area and strain accumulation, or the rate at which strain builds up in the rocks.
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, On seismograms, seismic waves recorded from more distant facilities are FARTHER APART than those recorded from facilities close to the epicenter
T or F- Surface waves are the first to arrive at a seismic facility
False, PRIMARY WAVES are the first to arrive at a seismic facility
The moment magnitude scale takes into account the size of an earthquake's
Fault rupture
The modified-Mercalli scale ranges from...
I to XII
About 15 percent of all earthquakes occur in the __________ ______, which stretches across Europe and Asia
Mediterranean-Asian Belt
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, you need 3 stations or more are needed to find the location of the epicenter.
Most other earthquakes occur on the crests of _____ ______
Ocean Ridges
Can pass through earths interior
P and S waves
To determine an epicentral distance, scientists consider the arrival times of what waves types?
P-Waves and S-Waves
Squeezes and pulls rock in the same direction as the wave travels
Primary waves
What is strain?
The deformation of a material in response to stress
What is stress?
The force per unit area acting on a material
On the stress-strain curve, what part of the curve represents the elastic deformation of a material? What part represents ductile deformation?
The lower straight segment of the curve represents the elastic defomation
What can happen during earthquakes in areas where the ground contains fluid-saturated sand?
The sand and subsurface materials may liquify and behave like quicksand, generating landslides and causing houses to fall and pipes to rise to the surface.
What is compression?
The stress that decreases the volume of a material
What takes place during the process called "pancaking"?
The supporting wall of the ground floor of a building fail and cause initially intact upper floors to fall and collapse. The debris resembles a stack of pancakes.
Studies of how waves reflect deep inside Earth show that Earth's inner core is solid
True
T or F- Seismologists have resoned that Earth's outer core must be liquid based on the disappearance of S-Waves
True
The P-Wave shadow zone does not recieve direct P-waves
True
Epicentral distance
When a quake occurs, a seismic monitoring station can determine how far away it was from the shock wave pattern -- that is called the "epicentral distance" -- but not the exact direction. But with three or more monitoring stations' epicentral distances, one can draw intersecting circles to pinpoint the exact location. the distance between the seismic station and the side
Most earthquakes occur near the _______ of techtonic plates.
boundaries
T or F - S-waves do not travel through Earth's mantle
false, S-waves travel through the upper mantle
Fracture along which movement occurs
fault
Fault surface along which movement takes place
fault plane
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
The Richter scale is a numerical scale use 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
mass
Fracture caused by horizontal tension
normal fault
Fracture that forms as a result of horizontal compression
reverse fault
Are rocks near earth's surface genrally brittle or ductile? Rocks at great depths?
rocks near earth's surface are brittle and rocks at great depths are ductile
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
Moment-magnitude values can be estimated from the...
seismic wave size
The focus of a catastrophic earthquake with high intensity values is almost always
shallow
Fracture caused by horizontal shear
strike-slip fault
Earthquake intensity depends primarily on the height of...
surface waves
What happens when stress exceeds the strength of a material?
the material fails
Seismic Station
the place at which earthquake waves are recorded. what records P and S waves three stations are needed to locate the focus and epicenter the center of the circle on the diagram
Epicenter
the point on the earth's surface vertically above the focus of an earthquake.
T or F - P-waves travel through Earth's mantle
true
T or F - Seismic waves change speed and direction when they encounter different materials
true
T or F- P-waves are bent when they strike the core
true