Science Chapter 19
Do brittle materials fail before or after plastic deformation occurs?
After
What is a surface wave?
Also known as L-waves (Last waves), they are the slowest of the three waves and they travel only along Earth's surface.
What is a primary wave?
Also known as P-waves, they squeeze and push rocks in the direction along which the waves are traveling. They are the first wave that you feel.
If an earthquake has a shallower focus depth, is it more likely to be mild or catastrophic?
Catastrophic
Would the two areas separated by the fault be closer together or farther apart after a reverse fault?
Closer
What are the three types of strain?
Compression, tension, and shear
How can time travel curves of Earthquakes inside Earth help learn about differences in composition and density in Earth?
Depending on where waves refract
Movement along a fault results in what?
Earthquakes
Would the two areas separated by the fault be closer together or farther apart after a normal fault?
Farther
What is the Richter scale?
It is a numerical rating system that measures the energy of large seismic waves.
Which seismic wave causes the most destruction?
L-Wave (Surface wave)
What is another effect can earthquakes have other than on man made structures?
Landslides
S-Waves do not travel through what?
Liquid
How did S waves help scientists figure out that Earth's core was partly liquid?
S-waves do not travel through liquid, and they never traveled through the core.
What is soil liquefaction?
Seismic waves cause almost fully saturated sand to behave like liquids
The locations of most earthquakes correspond closely with what?
Tectonic plate boundaries
What are the numbers in the Richter scale determined by?
The amplitude of the waves
The intensity of an earthquake depends on what?
The amplitude of the waves and the depth of its focus
What are earthquake hazards?
The factors that determine the severity of damage produced by an earthquake
What is a stress-strain curve?
The figure that forms when stress applied to a rock is plotted against the strain.
Ratings on the Richter scale increase by a factor of ____. Magnitude increases by a factor of ____ with every increase of one on the Richter scale.
10;32
What percent of earthquakes occur on the Circus Pacific Belt and what percent occur on the Mediterranean Belt?
80% and 15%
Explain how a tsunami occurs.
A fault occurs, and the water is moved upwards. When they reach shallow, water, they can form huge breakers.
What is a tsunami?
A large ocean wave generated by vertical motions on the seafloor from earthquakes
What is a secondary wave?
Also known as S-waves, they are named because they arrive second.
What is the modified Mercalli scale?
An earthquake scale that rates the type of damage and other effects as accounted by the observers. It uses Roman numerals.
What is the moment magnitude scale?
It is a rating scale that measures the energy released by an earthquake taking into account the size if the fault rupture, the movement along the fault, and the rock's stiffness.
What is a seismic gap?
It is a section located along faults that are known to be active, but have not experienced earthquakes in a long time.
What is a fault?
It is any fracture or system of fractures along which Earth moves.
What is elastic deformation?
It is caused when the a material is compressed, bent, or stretched and it returns to its original shape.
What happens when a P-Wave strikes the core?
It is refracted
What is shear?
It is stress that causes a material to twist.
What is tension?
It is stress that pulls a material apart.
What is strain?
It is the deformation of materials in response to stress.
What is magnitude?
It is the energy of seismic waves.
What is amplitude?
It is the height of a seismic wave.
What is a failure?
It is the point of rupture of a rock.
What is an epicenter?
It is the point on Earth's surface directly above the focus.
What is a focus?
It is the point where earthquake waves originate.
What is compression?
It is the stress that decreases the volume of a material.
What stress?
It is the total force acting on crustal rocks per unit of area.
What is plastic deformation?
It occurs when stress on an object builds up past the elastic limit and the object is subjected to permanent deformation.
Describe the Mexico City earthquake.
Medium sized buildings fell over because of the length of the seismic waves, but short and tall buildings were not affected.
What is the most commonly used scale for earthquakes?
Moment magnitude scale
As pressure increases, do rocks require a greater amount of stress to reach the elastic limit or less stress?
More
Most earthquakes are a result of what?
Movement of Earth's crust produced by plate tectonics
What is a seismometer?
Sensitive instruments that can detect vibrations from seismic waves
Do softer or harder materials have a greater risk for earthquake damage?
Softer
What is a seismic belt?
The long, narrow area in which most earthquakes occurs
What is pancaking?
The lower walls on a building fail to hold and the whole building falls down in layers
What is a normal fault?
The movement is partly vertical and partly horizontal. The horizontal movement pulls rocks apart and stretches the crust. Vertical movement causes one side to move down relative to the other.
The characteristics of earthquakes are determined by what?
The orientation and magnitude of stress applied to rocks and the strength of the rocks involved.
What is the elastic limit?
The point in which an object is put under so much stress that it is subjected to permanent deformation.
What is a seismogram?
The record produced by a seismometer
What is a fault plane?
The surface along which fault movement takes place
How does stress affect the movement along rock fractures?
There is movement along rock fractures when stress builds up.
What is a strike slip fault?
They are caused by shear movement
What are seismic waves?
They are the vibrations of the ground produced by earthquakes.
How do seismologists determine when an earthquake will occur?
They determine where seismic belts are located, and the areas that have had an earthquake the least recently have a higher risk. Also, if earthquakes occur repeatedly in what seems to be a pattern, they can be predicted. Also, the rate at which stress builds up plays a part.
How do seismologists determine the distance from a seismic station to the epicenter?
They measure the time difference between the P wave and S wave arrivals.
What is a global travel time curve?
They provide the average travel times of all P and S waves from wherever an earthquake occurs on Earth
What is a reverse fault?
Thye form as a result of horizontal and vertical compression that squeezes rock and creates a shortening of the crust. This causes rock on one side to be pushed up relative to the other. It can be seen near convergent plate boundaries.
What happens that makes a rock rupture?
When the stress increases to be greater than the strength of the rock