Transcript Earthquake Notes

When rock is under stress without
heat it deforms
Compression
Tension
Shearing
Yes! With great force or pressure rock can bend
and stretch!
Rock under stress with
great heat FOLDS
Any sudden movement of the crust
Plate boundaries…
Faults are places
where rocks move
past one another
AND sometimes NOT
on boundaries!
Normal Faults
Tension forces act in opposite directions.
One slab of the rock moves up, the other slab
down.
Most common at DIVERGENT boundaries
Reverse faults
Compression forces exist.
One block is pushed up and over the
other block.
Transform Fault
Produced where stresses are parallel to each
other.
Ex: San Andreas fault in California.
Plastic deformation-stress causes a fold
Elastic deformation-stress causes a fold and
then a break if the elastic limit is reached
If the rock goes back to normal spot, elastic
rebound spreads the energy in waves
Stress builds up at a fault
Elastic limit is reached & deformation happens,
causing an elastic rebound
An Earthquake is the release of energy (seismic
waves) from rock layers moving along a fault
Focus-underground origin of waves; actual
point of the shift
Epicenter-Closest point to the focus on the
earth’s surface (always directly above the focus)
Seismic waves are the release of energy
Body waves start at the focus and travel through
Earth
P waves
S waves
Surface waves start at the epicenter and travel
on the surface
L waves
1. In a uniform, homogenous medium, a
wave radiates outward at a certain
velocity.
2. The velocity of seismic waves depends
on the nature of the material it travels
through.
Increased density causes increased
velocity.
3. When waves travel from
one material to another,
they refract (bend) and
sometimes reflect
(bounce back).Density and
pressure are factors.
4. P waves are compressional waves and travel
through all media (gas, liquid, solid). S waves are
transmitted only through solids.
We get “shadow zones” on the globe where no
earthquake waves are measured as a result of the
bending and refracting
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Primary or pressure waves
Push-pull
Travel through solid & liquid (entire Earth)
Fastest
Particles move in a back & forth direction
In one direction
Radiating out from epicenter
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Secondary or shear wave
Travel only through solid (not liquid)
Move slower than P-waves
Particles move in a side to side motion
In one direction
Radiating out from epicenter
S waves lag behind P waves
Both can be easily
demonstrated with
a Slinky!
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Love wave (surface)
Travel only on the surface
Slowest but most destructive
Moves like an ocean wave – up, down, & around
Surface wave
Seismographs measure earthquake waves, P
first then S
Seismogram=
P-waves first
then S-waves
S waves lag behind P waves
Use triangulation with this
data
Use seismograms from 3
data stations
Find S-P lag time at all 3
spots
Use a compass to find the
distance of the epicenter to
each spot
3 circles overlap at 1 point
Can we use one? What would happen?
Can we use two? What would happen?
How does three help us?
Magnitude=Strength
energy an earthquake releases
Richter Scale from 1-10
We need to know the S-P lag time AND the
amplitude
Max height on a seismogram
Magnitude
S-P lag
Amplitude
Station A: ΔT = 40 s
390 km
Distance = ______
Station B: ΔT = 65 s
635 km
Distance = ______
Station C: ΔT = 33 s
Distance = ______
320 km
Station A: ΔT = 72s
Distance = 705
___ km
Station B: ΔT = 54s
Distance = 530
___ km
Station C: ΔT = 46s
Distance = 450
___ km
1. Label the beginning of the P-wave on the
seismogram.
2. Label the beginning of the S-wave on the
seismogram.
3. What is the lag time? _______
Identify the Richter Scale Magnitude of the earthquake?
Las Vegas Seismic Station
1.
What is the S-P lag time?
2.
What is the distance to the earthquake
epicenter?
3.
What is the S-wave amplitude?
4.
What is the magnitude using the nonogram?
6.7
Intensity is how people feel the earthquake
Measured on the Mercalli Scale
I-XII based on eyewitness accounts
Haiti
earthquake
What is the difference between
this scale and the Modified
Mercalli Intensity Scale (MMIS)?
List of greatest
magnitude
earthquakes
II-III
VII-VIII
VI
V
VI
IX
IX
VI
IX
IV
V
VII-VIII
V
IV
II-III
II-III
VII-VIII
VI
V
VI
IX
IX
VI
IX
IV
V
VII-VIII
V
IV
II-III
A series of ocean waves generated by
displacement on the ocean floor