Download Chapter 2 Earthquakes

I.
Chapter 2 Earthquakes
Earth’s Crust in Motion
A. Stress in the crust
An earthquake is the ___________and ___________ that results from the
movement of ___________ beneath the earth’s surface. Earth creates forces
that squeeze or pull the rock in the crust. These forces are examples of
__________ that force a rock to change it’s _________ or _______________.
B. Types of Stress
There are 3 different types of stress that occur in the _________. They are
______________, _______________ and ______________.
Shearing is rock moving in (#) _________ ____________ directions.
This can cause a rock to slip apart or change shape. __________ pulls on the
crust, stretching the rock so that the middle becomes thinner, kind of like
stretched bubblegum. Compression ___________ rock until it folds or breaks.
Deformation is caused by a _________ _________ in the Earth’s plates.
Deformation is any change in the volume or shape of the Earth’s crust.
C. Kinds of Faults
A fault is the break in _________ _________ that is created when stress
is built up, and the slabs of the earth slip past each other. Faults usually
take place along _________ ____________ where the plates compress,
shear or pull so much that they then break.
1. Strike slip fault-with this type of fault, the rocks _________ past each
other, but don’t make much up or down motion. A __________
______________ is where a strike-slip fault forms a boundary between 2
different plates. An example of a strike-slip fault, that is also a transform
boundary is the ________ _____________ __________.
2. Normal Faults- A normal fault is at an __________, so that one block
lies above, while the other lies ____________ the fault .When the fault
forms, the hanging walls slips down below the footwall. A fault that lies
above is a _________ ____________, and the fault that lies below is the
__________________. An example of a normal fault is the ___________
______________ ___________ ____________ in New Mexico.
3. Reverse Faults- a ______________ force produces reverse faults. A
reverse fault is the opposite of a ____________ fault. In this instance,
when the fault slips, the footwall falls below the ____________
_________.
D. Friction along faults
The way that a rock moves along a fault depends on the amount of
______________ between the 2 sides of the fault. Friction is how much
___________ there is between 2 objects.
E. Mountain building
1. An ____________ occurs when enough stress builds up between 2
faults. A valley forms when 2 __________ faults slide downward.
2. Folds are _________ in rocks when compressions __________ and
_____________ the earth’s crust.
3. A rock that folds upward, like an arch is called an _____________.
A rock that bends down to fold like a ____________ is called a
_________________.
4. A plateau is similar to a _____________ in that it has many
different layers that are wider than they are tall. A plateau is a
_______________ area of land which is above sea level.
II.
Measuring Earthquakes
The place that an earthquake starts is called the __________. This is the location
that is under great stress, which causes the stress to break. The spot directly
above the focus is called the _______________.
A. Seismic Waves
Earthquakes produce ___________that can be compared to a drumbeat. The
_______________ _____________ are the vibrations that are produced when
an earthquake occurs, which are produced by energy released by the
earthquake. They carry the energy away from the _____________, through
the ___________ of the earth, and across the __________.
The type of _________ and _________ will determine how much the earth
will shake. There are 3 types of waves: ______, ________ and _________
waves.
1. Primary Waves- These are the _____ waves to arrive. These make the
ground compress like an ___________. P waves can travel through both
liquids and ___________.
2. Secondary Waves- These are called secondary waves due to the fact that
they come ________. These move _______ to _________ and up and
down. When these waves reach the ground, they shake the earth violently.
S waves cannot travel through the medium of _________.
3. Surface Waves- These move more __________ than S and P waves, but
these cause the most ____________ movements of the ground.
B. Detecting Seismic Waves
1. Seismographs were used until recently, and record the measure of
___________ __________. These used a pen, and a rotating drum. When
the ground shakes, the pen will move, drawing lines in the form of a graph,
recording the movements created. Today scientists use ___________
_______________, which are used primarily in the same way.
C. Measuring Earthquakes
The 3 ways of measuring an earthquake are the ________ _________,
___________ __________, and ___________ ____________ ___________.
Magnitude measures how strong an earthquakes vibrations are based on
seismic waves long faults.
1. The Mercalli Scale
This was developed to measure an earthquakes ____________. This
ultimately describes how the earthquake affects people, places, and the land
surface. It is not a ___________ measurement.
III.
2. The Richter Scale
The Richter scale measures the size of __________ waves. This scale is good
for measuring earthquakes that are _________ but not those that are ________
or _________ away.
3. The Moment Magnitude Scale
The Moment Magnitude Scale estimates how much _________ was
_________ by an earthquake. This can be used to measure all earthquakes
near, far, and of different sizes. This also shows what kinds of _________
waves are produced and how ____________ they are.
D. Locating the Epicenter
The epicenter is located by using ________ ___________. The
____________ away the P and S waves are, the _________ the time, the
_______________ away the earthquake is. Where the 3 circles _________, is
where the location of the earthquake is.
Earthquake Hazards and Safety
A. How earthquakes cause damage-Earthquakes cause damage due to
________ _________. Near the epicenter ____ waves can cause severe
damage, due to the side-to-side motion. Earthquakes not only can cause
damage to buildings, but can also cause ____________ or
_____________.
1. Local soil conditions- _________ soil will shake more than tightly packed
soil. Houses that are built on solid rock, will shake less than those that are
built on sandy soil.
2. Liquefaction- occurs when soft sand gets turned to _______ due to the
violent shaking of the Earth. The liquefying of the solid soil is what is knows
as liquefaction. Liquefaction can cause ______________.
3. Aftershocks- Aftershocks is an earthquake that occurs when a larger
earthquake has hit an area. Aftershocks can occur ______, ________ or
___________ after the original earthquake has taken place.
4. Tsunamis- Tsunamis are caused by the _____________of the ocean floor,
when an earthquake has caused plate movement. A tsunami is a _________
__________ caused by water displacement due to the earthquake. The
tsunamis start at the ____________. The waves are not much greater in size
than normal waves, however as they get in more ____________ water, the
waves get ___________ together.
B. Making buildings safer- In order for buildings to be more apt to withstand
an earthquake, they need to be more __________, and __________.
1. Choice of location-Steep slopes can lead to the danger of a ___________
occurring. The __________ a building is from a fault the __________ strong
the shaking will be.
2. Construction methods-A building that rests on shock absorbing pads or
springs will have less energy from an earthquake reach them. This type of
building is called a _____-__________ building.
3. Protecting yourself during an earthquake-The 3 things to remember when
protecting yourself from an earthquake are to ________,________ and
IV
________. It is extremely important to be sure your ________ is covered,
which can be done by using your arms or a book.
Monitoring Faults
Earthquakes have been so regular in _________,_____________ that
geologists were able to regularly predict when earthquakes would occur,
however the pattern seems to have been broken.
A. Devices that monitor faults-When monitoring faults, __________ place
instruments that measure ____________ and __________ in the
__________ along faults.
1. Creep Meters-These can measure how much a fault has moved by
measuring the amount of _________ that has shifted against a measuring
scale. The creep meter stretches a wire across a fault to monitor the
___________ movement of the ground.
2. Laser-ranging devices- These use ___________ that detect _______ fault
movements. These will detect change in ___________ to the reflector.
3. Tiltmeters- measure the _________ of the __________. These detect
whether the land has _________ or ___________, even slightly. The liquid in
the tiltmeter will move from one ________ to the other.
4. Satellite monitors- These satellites have ___________ that make images
of _________. The satellite determines the __________ it takes for the
radio waves to make their trip to give accurate measurements of the
__________ to the ground.
B. Monitoring risk in the United States
Geologists are not able to predict earthquakes because they do not necessarily
always occur where stress has been built up along fault lines. Geologists do
know that earthquakes are likely where movement stores _________ in rock
along ________. They determine the risk of a possible earthquake based on
previous earthquakes, where there are active faults. The highest risk in the
United States for earthquakes are along the _________ _________, including
Washington, Alaska, and California.