Download Earthquake Notes

Earthquake Note Outline
I.
Earthquakes:
a. 1.1: Stress in Earth’s Crust
i. Introduction:
1. Enormous slabs of ______________________________ move unevenly over the
planet’s spherical surface, resulting in ______________________.
2. Stress – the force applied to an object.
3. Four types of stresses act on materials:
a. _________________________ stress – since the rock cannot move it
cannot deform.
b. _________________________ - squeezes rocks together, causing the
rocks to fold or fracture (most common at _______________________
plate boundaries)
c. __________________________ - rocks that are pulled apart, lengthen or
break apart (most common at ______________________________ plate
boundaries)
d. __________________________ - forces are parallel but move in opposite
directions (most common at ______________________________ plate
boundaries)
4. When stress causes a material to change shape, it has undergone ____________
or deformation
5. A rocks response to stress depends on the rock type
6. Rocks have three possible responses to increasing stress:
a. __________________________ deformation – the rock returns to its
original shape
b. __________________________ deformation – the rock does not return
to its original shape when the stress is removed
c. ___________________________ - the rock breaks
7. At the Earth’s surface, rocks usually break quite _______________________
8. Deeper in the crust rocks are more likely to deform plastically
9. Sudden stress (like hitting it with a hammer) is more likely to make a rock break
10. Stress applied over time often leads to plastic ____________________________
ii. Geologic Structure:
1. _________________________ rocks are important for deciphering the geologic
history.
2. Sedimentary rocks are formed with oldest layer on the ___________________
and the youngest on _________________
3. You can trace the deformation a rock has experienced by seeing how it differs
from its original horizontal oldest-on-bottom position
4. This deformation produces geologic structures as ________________, joints, and
faults that are caused by stress
5. _____________________ - occur when rocks deforming plastically under
compressive stresses crumple.
a. They do _______________ return to their original shape
6. A rock under enough stress will ____________________. If there is no
movement on either side of a fracture, the facture is called a
__________________.
7. If the blocks of rock on one or both sides of a fracture move, the fracture is
called a ______________________.
a. Sudden motions along faults cause rocks to break and move suddenly.
The energy released is an _________________________.
8. __________________ - the distance rocks move along a fault
9. Normal Fault – the hanging wall drops down relative to the footwall
10. Reverse Fault – the footwall drops down relative to the hanging wall
11. Thrust Fault – a type of reverse fault in which the fault plane angle is nearly
horizontal
12. ___________________ faults can be huge!
13. They are responsible for uplifting mountain ranges in regions experiencing
tensional stress.
14. Strike-slip Fault – a dip-slip fault in which the dip of the fault plane is vertical
a. Strike-slip faults result from _____________________ stresses
b. California San Andreas Fault is the world’s most famous
________________________________ fault.
iii. Stress and Mountain Building:
1. Two _____________________________ continental plates smash upwards to
create mountain ranges.
2. Subduction of oceanic lithosphere at convergent plate boundaries also builds
mountain ranges.
b. 1.2: The Nature of Earthquakes:
i. Introduction:
1. An _________________________________ is a sudden ground movement
caused by the sudden release of energy stored in rocks
2. The energy is transmitted by ___________________________ waves
ii. Causes of Earthquakes:
1. The description of how earthquakes occur is called the elastic
________________________
2. Focus – the _____________________ point where the rocks rupture IN the crust
3. Epicenter – the point on _____________________ (surface) that is directly
above the focus
4. Shallow earthquakes cause the ________________ damage because the focus is
near where people live.
5. The epicenter of an earthquake is what the media and the scientists report.
iii. Earthquake Zones:
1. About 80% of all earthquakes strike around the ___________________ Ocean
basin because it is lined with convergent and transform boundaries.
2. Transform plate boundaries:
a. Deadly earthquakes occur at _____________________________ plate
boundaries
b. Transform faults have shallow ____________________ earthquakes
3. Earthquakes at ________________________ plate boundaries mark the motions
of subducting lithosphere as it plunges through the mantle
4. Eventually the plate heats up enough to ________________ plastically and the
earthquake stops
5. _____________________________ plate boundaries produce earthquakes all
around the Pacific Ocean
6. Massive earthquakes are the hallmark of the thrust faulting and folding when
____________ continental plates converge.
7. March 2011, and enormous _________________ earthquake struck off of Sendai
in northwestern Japan.
a. Was the most powerful event to strike Japan and one of the top
_________ known in the world.
b. Damage from the earthquake was nearly overshadowed by the tsunami it
generated.
c. Two months after the earthquake about 250,000 people were dead or
missing, and 125,000 buildings had been damaged or destroyed.
d. Aftershocks, some as large as major earthquakes, have continued to rock
the region.
8. The Pacific Northwest of the United States is at risk from a potentially massive
earthquake that could strike at any time!
9. Earthquakes at _____________________________ ridges are small and shallow
because the plates are young, thin, and hot.
10. On land where _____________________________ split apart, earthquakes are
larger and stronger
11. Intraplate earthquakes are the results of stresses caused by plate
_______________________ acting in solid slabs of lithosphere
iv. Seismic Waves:
1. ______________________ is transmitted in waves – seismic waves
2. Semiologist use seismic waves to learn about __________________________
and also to learn about Earth’s interior.
3. The two types of seismic waves:
a. Body Waves (P-waves and S-waves) – because the move through the
______________ of the Earth – produce sharp jolts
b. Surface Waves – travel along the ______________________, outward
from an earthquake’s epicenter – the dolling does most of the damage in
an earthquake
v. Tsunami:
1. ______________________ - deadly ocean waves from an earthquake
2. The sharp jolt of an undersea quake forms a set of waves that travel through the
sea entirely unnoticed
3. When they come onto _______________, they can grow to enormous heights
4. Boxing Day Tsunami (December 26, 2004) was by far the deadliest of all time
a. Was caused by the 2004 Indian Ocean Earthquake (magnitude of 9.2) and
was the second largest earthquake ever recorded
b. About 230,000 people died in eight countries
c. As a result of the 2004 tsunami, an Indian Ocean warning system was put
into operation in June 2006
c. 1.3: Measuring and Predicting Earthquakes:
i. Introduction:
1. Seismograms record _______________________ waves
2. The currently accepted method is the moment _______________________
scale, which measures the total amount of energy released by the earthquake
3. At this time, semiologists have not found a reliable method for predicting
earthquakes.
4. Seismograph – produces a graph-like representation of the ______________
waves it receives and records them onto a seismogram
a. Contain information that can be used to determine how strong an
earthquake was, how long it lasted, and how far away it was.
5. Seismometers – record ground motions using _____________________ motion
detectors
6. If a seismogram records P-waves and surface waves but NOT S-waves, the
seismograph was on the other side of the Earth from the earthquake
7. The ________________________ of the wave can be used to determine the
magnitude of the earthquake.
ii. Finding the Epicenter:
1. To locate an earthquake epicenter:
a. Scientists first determine the ____________________________ distance
from three different seismographs. The longer the time
________________________ the arrival of the P-wave and S-wave, the
farther away is the epicenter
b. The scientist then draws a circle with a radius equal to the distance from
the epicenter for that seismograph. The epicenter is somewhere along
that circle. This is done for _____________ locations.
i. Where the circles intercept that is where the earthquake
occurred.
iii. Earthquake Intensity:
1. People have always tried to quantify the size of and _____________________
done by an earthquake.
2. Three methods:
a. Mercalli _______________________ Scale – earthquakes are described
in terms of what nearby residents felt and the damage that was done to
nearby structures.
b. ______________________ Magnitude Scale – uses a seismometer to
measure the magnitude of the largest hold of energy released by an
earthquake.
c. _______________________ Magnitude Scale – measures the total
energy released by an earthquake and calculated from the area of the
fault that is ruptured and the distance the ground moved along the fault.
3. Richter Scale and Moment Magnitude scales are logarithmic:
i. The amplitude of the largest waves _______________________
tem times from one integer to the next
ii. These two scales often give very similar measurements
4. Which scale do you think is best?
a. With the Richter Scale, a ________________________ sharp jolt
measures higher than a very long intense earthquake that release more
energy.
b. The moment magnitude scale more accurately reflects the energy
released and the damage caused.
c. Most semiologist now use the_________________________ magnitude
scale.
5. Magnitude ___________ earthquakes are rare!!!
Location
Year
1980
Magnitude
9.5
Prince William Sound, Alaska
1964
9.2
Great Indian Ocean Earthquake
9.3
1952
9.0
2011
9.0
iv. Earthquake Prediction:
1. Scientists are a ___________________ way from being able to predict
earthquakes.
2. A good prediction must be _________________________ as to where an
earthquake will occur, when it will occur, and at what magnitude it will be so
that people can evacuate.
3. __________________________ an earthquake will occur is the easiest feature to
predict.
4. Earthquake prone communities should always be prepared for an earthquake.
These communities can implement building codes to make structures
earthquake safe.
5. __________________________ an earthquake will occur is more difficult to
predict.
6. Earthquakes should occur at regular intervals BUT so far scientists cannot predict
when quakes will occur even to within a few years.
7. Signs sometimes come before a large earthquake. Small quakes, called
________________________, sometimes occur a few seconds to a few weeks
before a major quake.
a. Many earthquakes do not have foreshocks and small earthquakes are not
necessarily followed by a large earthquake.
b. Often, the __________________________ around a fault will dilate as
microfractures form.
c. Ground titling, caused by the buildup of _____________________ stress
in the rocks, may precede a large earthquake, but not always.
d. Water levels in wells fluctuates as water moves into or out of
__________________________ before an earthquake.
e. The relative arrival of P-waves and S-waves also decrease just before an
earthquake occurs.
f. Folklore – tells of _____________________ behaving erratically just
before an earthquake
g. If indeed animals sense danger from earthquakes or tsunamis, scientists
do not know what it is they could be sending, but they would like to find
out.
v. EARTHQUAKE PREDICTION IS VERY ____________________________ AND NOT VERY
_____________________________, BUT SCIENTISTS ARE LOOKING FOR A VARIETY OF
CLUES IN A VARIETY OF LOCATIONS AND TO TRY TO ADVANCE THE FIELD!
d. 1.4: Staying Safe in Earthquakes:
i. Introduction:
1. Earthquakes are ______________________ disasters that cause enormous
amounts of damage, second only to ____________________________.
2. Safe construction techniques, securing heavy objects, and preparing an
emergency kit are among the precautions people can take to minimize damage.
3. Earthquakes kill people and cause property damage. The damage depends
somewhat on the earthquake _______________________ but mostly on the
_________________________ of the structure.
4. Structures falling on people injure and kill them. More damage is done and more
people are killed by the _________________ that follow an earthquake than the
earthquake itself.
ii. What Makes An Earthquake Deadly?:
1. Population _____________________ - more people in an area the more they
could be killed.
2. Not the size of the earthquake – think about population density
3. __________________________ Type – sediments that are saturated with water
and undergo __________________________________ and become like
quicksand. Soil on a hillside may become a landslide.
4. In earthquake prone areas, city planners try to reduce hazards.
iii. Earthquake Safe Structures:
1. Skyscrapers and other large structures built on soft ground must be
____________________ to bedrock, even if it lies hundreds of meters below the
ground surface.
2. The correct building material must be used. Houses should bend and sway.
3. Larger buildings must sway, but not so much that they touch nearby buildings.
a. Counterweights and diagonal steel beams are used to hold down sway.
b. _________________ buildings can be placed on rollers so they can move
with the ground.
c. ______________________________, such as where the walls meet the
foundations, must be made strong.
d. In a multi-story building, the first story must be well supported.
4. Elevated freeways and ______________________ can also be retrofitted so that
they do not collapse.
5. ________________________ often cause more damage than the earthquake.
a. Fires start because seismic waves rupture gas and electrical lines and
breaks in water mains make it difficult to fight the fires.
6. Cost – more sturdy structures are much more expensive to build.
iv. Protecting Yourself In An Earthquake:
1. Before:
a. Have an engineer evaluate the house for structural integrity
b. Bracket or ______________________ brick chimneys to the roof
c. Prepare an earthquake kit with three days’ supply of water and food, a
radio, and batteries.
d. Place flashlights all over the house and in the glove of your car.
e. Be sure to have a first aid kit
f. Plan in advance how you will evacuate and where you will go.
2. During:
a. If you are in a building, get ______________________ a sturdy table,
cover your head, and hold on.
b. Stay away from windows, mirrors, and large furniture.
c. If the building is structurally unsound, get outside as fast as possible
d. If you are outside, run to an open area away from building and power
lines that may fall.
e. If you are in a car, stay in the car
3. After:
a. Be aware that _______________________________ are likely
b. Avoid dangerous areas like hillsides that may experience a landslide
c. Turn off water and power to your home
d. Use your phone only if there is an emergency
e. Be prepared to wait for help or instructions. Assists other as necessary.