Real- Time Earthquake Data
http://earthquake.usgs.gov/
EQs
EQ = Movement of E’s lithosphere that occurs when rocks in
the lithosphere suddenly shift, releasing stored energy.
EQs occur b/c stress forces of have exceeded the strength of
rock.
Stress builds when rocks along 2 sides of a fault snag and
lock (friction)
as stress builds – so does POTENTIAL ENERGY IN
ROCKS
When rocks are strained beyond limit – they break & move.
(Potential  Kinetic Energy in form of seismic waves)
Stress & Strain on Rocks
Stress – Force that squeezes rocks
together, pulls them apart, pushes in diff.
directions.
Stress causes strain or deformation
(change in shape or volume) of rock
Stress
Does not exceed rock
strength
Folds
Exceeds rock strength
Faults
Stress
Does not exceed rock
strength
Folds = Bending rock
layers
High Temps. &
Pressure
Exceeds rock strength
Faults = Breaks in rock
layers & movement
along breaks
Low Temp. & Pressure
– Near Crust
Folds
Anticline = up facing fold
Syncline = down ward facing fold
Faults
Types of Faults
1. Dip – Slip
Motion up or down fault
surface
a. Reverse or Thrust:
Hanging wall moves UP.
b. Normal: Hanging wall
moves DOWN
http://www.windows.ucar.edu/tour/link=/earth/geology/fault.html
Types of Faults
2. Strike – slip
Sliding – Horizontal
Movement
3. Oblique – slip
dip-slip & strike slip
combined
Plate
Boundary:
Interpretation of Tectonic History
Convergent
Thrust/Reverse
Divergent
Normal
Transform
Strike-Slip
EQ Vibrations
•EQ vibrations begin at a
point called a FOCUS.
•Vibrations travel from focus
through the earth’s crust as
waves.
•Surface directly above the
focus is called the epicenter.
•These waves can be
detected and measured on
earth’s surface with a
SEISMOGRAPH.
SEISMOGRAPHS
Instrument that
measures &
records EQ
waves.
Strength of EQ
waves is
referred to as
MAGNITUDE.
Wave Motion:
http://sunshine.chpc.utah.edu/labs/seismic/index.htm?ASPIRE_Session
=964f1ed30b7e49ceb81bd77f444d9230
3 Types of Seismic Waves
1. Primary Waves (P waves)
2. Secondary Waves (S waves)
3. Surface Waves
Each wave originates from the FOCUS of
the earthquake.
Each wave travels in a different way, at
different speeds, and causes different
amounts of destruction.
Seismic Waves = vibrations produced by energy
released during EQ
P Waves: Primary
Wave
•Arrives 1st & Travels
FASTER
•Longitudinal / Travel in
direction of wave motion.
•Compress & Expand
like accordion (like
sound waves)
•Move through Solids &
Liquids
Virtual EQs http://www.sciencecourseware.org/VirtualEarthquake/VQuakeExecute.html
Seismic Waves http://www.geo.mtu.edu/UPSeis/waves.html
Seismic Waves
S Waves – Secondary
• Transverse –
Material vibrates
perpendicular (rt
angles) to wave
motion
• What you FEEL in
an EQ
• Rock moves up &
down or side to side
• Arrive after P
• Move only through
SOLIDS
•
Seismic Waves: Surface
Waves
Surface Waves develop when vibrations reach
surface
• Slower than P waves
• Most destructive – Different types of motion
•
More P & S wave animations: http://www-rohan.sdsu.edu/~rmellors/lab8/l8maineq.htm
•
Video clip: http://news.bbc.co.uk/1/hi/sci/tech/4126809.stm
Rating Earthquakes
Earthquakes are rated in terms of
MAGNITUDE or INTENSITY by different
scales.
1. Moment Magnitude Scale
2. Richter Scale
3. Mercalli Scale
Moment Magnitude Scale
Uses a seismogram
Rates on scale from 1- 10
Looks at Eqs in terms of ENERGY
Each # releases 31 times more ENERGY than the
# before it.
• Example
A 6 releases 31 times more energy than a 5, and
a 5 releases 31 times more energy than a 4.
The energy difference between a 4 and a 6 EQ
on the richter scale is 31 X 31 = 961
How much more energy does a 7.5
release compared to a 4.5?
• Show your work here.
Richter Scale
• Uses a seismogram
• Rates on scale from 1- 10
• Looks at Eqs in terms of the SIZE OF THE
WAVES
1 – 3: Small earthquake waves – very little
shaking
4 – 6: Moderate earthquakes – noticeable shaking
and some damage
7 - 10+ BIG Earthquakes – Very destructive
Measuring EQs
Mercali Intensity Scale
•Measures observed effects of
Earthquake on a 1 – 12 scale
•Degree of shaking and damage
•Not an actual measure of seismic
waves
Link
•http://www.abag.ca.gov/bayarea/eqmaps/doc/mmi.html
Mercali Intensity Scale
•Measures observed RESULTS of
Earthquake on a 1 – 12 scale
•Degree of shaking and DAMAGE to
structures
•Don’t need a seismogram
Link
•http://www.abag.ca.gov/bayarea/eqmaps/doc/mmi.html
EFFECTS OF EQs
•Deaths & Injuries – but mostly from
collapsing structures
•Damage to buildings & structures
(collapse)
•Underground water and gas pipes break –
floods & fires
•Landslides
•Tsunamis
Seismic Waves are used to Study
Earth’s Interior
P and S waves are
“bent” and their
velocities are
affected as they
move through
material of varying
density
Link:
http://sunshine.chpc.utah.edu/labs/seismic/index.htm?ASPIRE_Sessi
on=964f1ed30b7e49ceb81bd77f444d9230
1. What type of fold is shown here? (Anticline or Syncline)
2. Would these folds be created in a DUCTILE (high temp. & pressure,
deeper in crust) or BRITTLE (low temp & pressure, at surface)
environment?
3. These folds in Newfoundland New Jersey would have be
produced …
a.
b.
c.
d.
When Pangaea assembled ~ 240 Ma.
When Pangaea broke apart ~ 100 Ma
During the ice age as glacial ice sheets retreated ~ 10 Ka
They are currently being produced by New Jersey’s current
tectonic activity.
4. Support your answer to #2 with a reason.
5. Is this a dip-slip or strike slip fault? If dip-slip – say what type of dip-slip
(Thrust or Normal).
6. Is this fold produced by compressional; extensional; or shearing forces?
7. What type of plate boundary would you expect to find these faults?
(Convergent; Divergent; Transform)
8. Which fault would be produced by
shearing forces?
9. Would fault H be made in an ancient
rift valley or a mountain building
zone? Support your answer with a
reason.
10. A. What type of fault can you see in this picture ?
B. Could this location be an ancient subduction zone? Why or why not?
11. A. What type of fault can you see in this picture ?
B. What type of plate boundary produces these faults?
12. A. What type of fault can you see in this picture ?
B. Could this location be an ancient convergent plate boundary? Why or
why not?
13. A. What type of fault can you see in this picture ?
B. What type of forces produced this fault? (There are 2 forces)
Latest Quakes
http://earthquake.usgs.gov/eqcenter/recente
qsww/Quakes/quakes_all.php
Top Ten Lists
http://earthquake.usgs.gov/eqcenter/top10.p
hp
Links
Virtual Earthquakes
http://www.sciencecourseware.org/VirtualEarthquake/VQuakeExecute.
html
Wave Types http://www.geo.mtu.edu/UPSeis/waves.html
Triangulation & “Hearing EQs”
http://www.seismo.unr.edu/ftp/pub/louie/class/100/seismic-waves.html
More virtual seismograms
http://www-rohan.sdsu.edu/~rmellors/lab8/l8maineq.htm
Earthquakes outline subducting slab – Interactive Web Lab
http://openlearn.open.ac.uk/mod/resource/view.php?id=172185