1	Earthquakes
2	Earthquakes What ‘is’ an earthquake? Sudden release of energy, in form of waves, caused by movement of rocks along a fault. When the amount of stress on rock exceeds elastic properties, the Rock breaks Why do they happen? Ultimately, due to Stress & Friction Forces (stress) on faults is continuous; movement is not. Elastic rebound Rock subjected to stress as plates move Rocks bend and store energy Slippage on fault causes rock to spring back to original shape releasing energy in form of seismic waves
3	Elastic Rebound
4	Earthquakes- Why does the earth shake? When the blocks slip at the time of an earthquake, the vibrations are called seismic waves Seismic energy propagates in waves S Wave- slower, moves through solid material P Wave- faster, moves through liquid & solid Each Wave has an amplitude & frequency.
5	Earthquake Lingo….. Epicenter- initial site, at surface Location on the surface of the earth directly above the focus Focus- initial site, at depth Location of the source of the earthquake within the earth
6	Earthquake epicenter Can determine distance to epicenter of earthquake Distance determined by difference in arrival time of p and s waves Direction determined by triangulation Need 3 or more seismic stations
7	Finding the Location of an Earthquake
8	Hazards associated with Earthquakes Ground rupture Flooding Fires (due to gas leaks) Ground motion and building collapse Liquefaction Water rich sediment liquefies, and highly accentuates ground motion Can act like quicksand, or send geysers of water & sand into the air i.e.. San Francisco Tsunami’s a very large ocean wave that is created by a submarine earthquake or volcanic eruption Aftershocks do as much or more damage than the original earthquake! Landslides
9	Liquefaction, San Fransisco
10	Effect of Underlying Material
11	Alaska, 2002
12	Alaska, 2002
13	Landslides Caused by 1964 Alaskan Quake
14	2004 Indian Ocean Earthquake and Tsunami Extremely powerful earthquake Fault segment 1200 km long, est. 100 km wide moved upwards about 3-4 m, 15 m along subduction zone Magnitude 9.15, fourth largest in last 100 years Equivalent to 100 gigatons of TNT Tsunami Moved at 500 to 1,000 km/h in open ocean Slowed to 20-30 km/h when hit, but 24-30 m high Destroyed swath up to 2 km wide along coast in Indonesia Effects Up to 310,000 people dead in Asia and Africa More than 1.5 million displaced One of ten worst earthquakes and the worst tsunami in recorded history
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18	Measuring an Earthquake Earthquakes meaured by Intensity and magnitude Intensity measured by Seismographs Intensity is measured using the Mercalli Scale Measures the EFFECTS of an earthquake. Older scale, based on human observation Not always reliable, because damage affected by population density, building design, and material present at surface Magnitude evaluated by Scales Richter Scale Measures the SEISMIC ENERGY released by an earthquake Logarithmic. Each magnitude is 10x greater than the last
19	Earthquake Intensity
20	Earthquake Magnitudes
21	10 Largest Earthquakes in Recent History Chile, 1960 9.5 Richter Alaska, 1964 9.2 Richter Russia, 1952 9.0 Richter Ecuador, 1906 8.8 Richter Alaska, 1957 8.8 Richter Kuril Islands, 1958 8.7 Richter Alaska, 1965 8.7 Richter India, 1950 8.6 Richter Chile, 1922 8.5 Richter Indonesia, 1938 8.5 Richter