Real- Time Earthquake Data

http://earthquake.usgs.gov/

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

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.

•Compress & Expand like accordion (like sound waves)

•Move through Solids & Liquids

•Least destructive

Seismic Waves S Waves – Secondary

• What you FEEL in an EQ

• Rock moves up & down or side to side (Snake-like)

• Arrive after P

• Move only through SOLIDS

Seismic Waves: Surface Waves

• Surface Waves develop when vibrations reach surface

• Slowest waves• Most destructive, most damaging

• 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 is 31 X 31 = 961

Moment Magnitude Scale

• Uses a seismogram

• Rates on scale from 1- 10

• Looks at Eqs in terms of the SIZE OF THE WAVES

• Each # has waves 10x bigger than previous #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

Mercali Intensity Scale

•Measures observed RESULTS or DAMAGE 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

•Damage to buildings & structures

•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

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