Earthquakes - Seismology Earthquake – The release of energy (seismic waves) from rock layers moving along a fault

Kobe, Japan Earthquake January 17, 1995

1994 Northridge earthquake (near LA) – 6.7 M 1989 Loma Prieta earthquake (Bay Bridge) near San Francisco (6.9 M)

1960 Chile earthquake (9.5 M) – highest ever recorded 1964 Alaskan earthquake (9.2 M) – 2nd highest ever

2010 Haiti earthquake (7.0 M) Dec 26th 2004 tsunami earthquake (9.1 M)

What causes an earthquake? STRESS!!! Plastic Deformation AND Elastic Deformation Stress builds along a fault causing elastic deformation & then an earthquake (elastic rebound)

Where do earthquakes occur? Faults - a break in rock where movement occurs Plate Boundaries (most of the time) Interior of Plates (sometimes) Recent California Earthquakes: http://scedc.caltech.edu/recent/index.html Interesting Facts: There are about 1,000,000 earthquakes a year; ONLY about 20 are considered severe

Focus vs. Epicenter

Seismic Body Waves: P vs. S Waves Body Waves move through the Earth & start at the Focus P waves – Primary Wave push-pull motion; fastest wave; travel through solids & liquids S waves Secondary Wave side to side motion; slower than P wave; cannot travel through liquid

Seismic Wave Simulations http://www.sims.scienceinstruction.org/earthquake/index. html

Surface Seismic Waves Surface waves – travels across Earth’s surface; starts at the epicenter; are slow moving, do not travel as far & cause the most damage (L wave)

Seismographs vs. Seismograms Seismogram example Seismogram S-P Lag Time Example: www.sciencecourseware.com/eec/Earthquake/

Locating an Epicenter Determine S-P lag time Use Travel-Time Graph to determine distance to epicenter Use compass to pinpoint epicenter Need three locations to TRIANGULATE the epicenter location

Virtual Earthquake Class Example www.sciencecourseware.org/VirtualEarthquake/VQuakeExecute.html Select Japan OR Southern California