Earthquakes What is an earthquake? What can we learn from earthquakes? How do we measure earthquakes? Can we predict earthquakes?

What is an earthquake? An earthquake is a vibration of the earth due to a rapid release of energy. The energy travels out from the epicenter in waves.

What can we learn from earthquakes? Origins of earthquakes were unknown until 1855 (faults) Mechanisms of earthquakes were unknown until H.F. Reid conducted a study following the 1906 San Francisco earthquake. Earthquakes happen after rock is bent and stretched to its limits due to tectonic plate movement.

Faults Normal Reverse Strike-Slip

San Francisco Earthquake of 1906 8.3 on Richter Scale 7.8 on Moment Magnitude Scale Major structural damage caused by earthquake Total destruction caused by fires after earthquake

San Francisco 1906 http://findaid.oac.cdlib.org/findaid/ark:/13030/tf0q2nb1hm

San Francisco 1906 http://findaid.oac.cdlib.org/findaid/ark:/13030/tf0q2nb1hm

San Francisco 1906 http://findaid.oac.cdlib.org/findaid/ark:/13030/tf0q2nb1hm

San Francisco 1906 http://findaid.oac.cdlib.org/findaid/ark:/13030/tf0q2nb1hm

San Francisco 1906 http://findaid.oac.cdlib.org/findaid/ark:/13030/tf0q2nb1hm

Other Large Earthquakes 1556 China (deadliest) 1886 South Carolina (Eastern USA largest) 1960 Chile 9.6 Magnitude (largest) 1964 Alaska 9.2 Magnitude (N.A. largest) 2006 Hawaii 6.7 (most recent significant earthquake in U.S.) http://earthquake.usgs.gov/

Measuring Earthquakes Seismographs use the property of inertia to measure the strength of earthquakes The recorded pattern of an earthquake is called a seismogram The seismograph records P waves first, then S waves, and finally Surface waves. Three seismographs can triangulate the epicenter of an earthquake

Triangulate Epicenter 3 seismographs are used to pinpoint the epicenter which is directly above the focus of the earthquake http://www.calstatela.edu/faculty/acolvil/quakes/epi_location.jpg

Body Waves Travel through the interior of the Earth http://www.bgr.bund.de/EN/Themen/Seismologie/Bilder/Sei__seis__ctbto__g,property=default.jpg

P Waves Primary waves move faster Compression waves- the material travels parallel to the wave direction Travel through solids, liquids, and gasses

http://www.geo.mtu.edu/UPSeis/waves.html

S Waves Secondary waves move slower Transverse wave- the material moves perpendicular to the wave direction Travels through solids but not liquids or gasses

http://www.geo.mtu.edu/UPSeis/waves.html

Surface Waves Surface waves travel along the surface of the earth spreading out from the earthquakes epicenter Love- Side to side Rayleigh- elliptical motion similar to water waves

http://www.geo.mtu.edu/UPSeis/waves.html

http://www.geo.mtu.edu/UPSeis/waves.html

Measuring Earthquakes Modified Mercalli Intensity Scale Uses damage to determine strength I-XII Richter Scale (ML) measures according to amplitude of vibration Moment Magnitude Scale (MW) Measures displacement along a fault zone Better for large earthquakes

Earthquakes Most Earthquakes occur around the circum-Pacific belt. (Ring of Fire) Liquefaction may add to damage of earthquakes

Liquefaction http://www.ce.washington.edu/~liquefaction/html/quakes/niigata/niigata.html

Liquefaction http://www.ce.washington.edu/~liquefaction/html/quakes/niigata/niigata.html

Triggered By Earthquakes Tsunamis Tsunami Flash Warning System Flash Landslides Fire

Earth’s Layers Core Mantle Crust Iron Nickel Alloy Solid Rocky Perdidotite Crust Thin rocky layer of mostly Basalt

Earth’s Layers Inner Core- solid metal alloy Outer Core- molten metal alloy Mesosphere- high pressure, gradual flow of solid rock Asthenosphere- high temp, soft weak layer Lithosphere- rigid structure, “floats” on upper asthenosphere

Predicting Earthquakes Short Range (hours or days) Efforts are made to monitor strain, uplifting, and subsidence in order to predict earthquakes. Need more reliable means of prediction. Long Range (years or hundreds of years) Probability based on past events Helps in engineering buildings

Earthquake Mitigation http://www.odditycentral.com/videos/worlds-largest-earthquake-damper.html http://www.youtube.com/watch?v=NYSgd1XSZXc&feature=related

Resources www.sciencecourseware.org http://earthquake.usgs.gov/learning/ http://www.wwnorton.com/earth/egeo/index/animations.htm http://earthsci.org/education/teacher/basicgeol/earthq/earthq.html#Earthquakes