real- time earthquake data
TRANSCRIPT
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)
EQs
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
Folds Faults
Does not exceed rock strength
Exceeds rock strength
Stress
Folds = Bending rock layers
Faults = Breaks in rock layers & movement along breaks
Does not exceed rock strength
Exceeds rock strength
High Temps. & Pressure
Low Temp. & Pressure – Near Crust
Folds
Anticline = up facing foldSyncline = down ward facing fold
Faults
Types of Faults
http://www.windows.ucar.edu/tour/link=/earth/geology/fault.html
1. Dip – SlipMotion up or down fault surface
a.Reverse or Thrust: Hanging wall moves UP.
b. Normal: Hanging wall moves DOWN
Types of Faults
2. Strike – slip
Sliding – Horizontal Movement
3. Oblique – slipdip-slip & strike slip combined
Interpretation of Tectonic History
Divergent Transform
Plate Boundary:
Convergent
NormalThrust/Reverse Strike-Slip
•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.
EQ Vibrations
Instrument that measures & records EQ waves. Strength of EQ waves is referred to as MAGNITUDE.
SEISMOGRAPHS
Wave Motion: http://sunshine.chpc.utah.edu/labs/seismic/index.htm?ASPIRE_Session=964f1ed30b7e49ceb81bd77f444d9230
3 Types of Seismic Waves1. 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
Virtual EQs http://www.sciencecourseware.org/VirtualEarthquake/VQuakeExecute.html
Seismic Waves http://www.geo.mtu.edu/UPSeis/waves.html
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
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
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
Moment Magnitude Scale
How much more energy does a 7.5 release compared to a 4.5?
• Show your work here.
• 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
Richter Scale
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 wavesLink
•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 seismogramLink
•http://www.abag.ca.gov/bayarea/eqmaps/doc/mmi.html
•Deaths & Injuries – but mostly from collapsing structures
•Damage to buildings & structures (collapse)
•Underground water and gas pipes break – floods & fires
•Landslides
•Tsunamis
EFFECTS OF EQs
Seismic Waves are used to Study Earth’s Interior
Link: http://sunshine.chpc.utah.edu/labs/seismic/index.htm?ASPIRE_Session=964f1ed30b7e49ceb81bd77f444d9230
P and S waves are “bent” and their velocities are affected as they move through material of varying density
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. When Pangaea assembled ~ 240 Ma.
b. When Pangaea broke apart ~ 100 Ma
c. During the ice age as glacial ice sheets retreated ~ 10 Ka
d. 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/recenteqsww/Quakes/quakes_all.php
Top Ten Lists
http://earthquake.usgs.gov/eqcenter/top10.php
LinksVirtual Earthquakeshttp://www.sciencecourseware.org/VirtualEarthquake/
VQuakeExecute.htmlWave Types http://www.geo.mtu.edu/UPSeis/waves.htmlTriangulation & “Hearing EQs”http://www.seismo.unr.edu/ftp/pub/louie/class/100/seismic-waves.htmlMore virtual seismogramshttp://www-rohan.sdsu.edu/~rmellors/lab8/l8maineq.htmEarthquakes outline subducting slab – Interactive Web Labhttp://openlearn.open.ac.uk/mod/resource/view.php?id=172185
