EARTHQUAKES 1988 Armenian Earthquake – Spitak Communications Building USGS

EARTHQUAKES Occur in all plate boundaries  Diverging  Converging  Continent/ocean (Subduction)  Ocean/ocean (Subduction)  Continent/continent (Collision)  Transform

PLATE BOUNDARIES

WORLD WIDE DISTRIBUTION OF EARTHQUAKES

Earthquakes Terms  Focus – point within the earth where initial slip is generated  Epicenter – point on the earth’s surface directly above the focus  Seismic waves - move outward from focus

SEISMIC WAVES

P-WAVE (Primary)  Fastest seismic  Travels through liquids and solids inside the Earth  Compresses and expands in the direction of wave movement. Tasa

S-WAVE (Secondary)  2 nd fastest  Travels through solids inside the earth  Moves with a shearing motion perpendicular to wave travel TASA

SURFACE WAVES  Slowest wave  Travels on the earth’s surface  Moves with an elliptical motion or shearing  Potentially most destructive TASA

Earthquake Waves

MEASURING EARTHQUAKES TASA

Seismograph

SEISMIC WAVE – TRAVEL TIME Amount of time between P and S waves are directly related to distance to the epicenter Tarbuck &Lutgens

LOCATING AN EARTHQUAKE 3 Seismic Stations Required Press & Siever

MEASURING EARTHQUAKES INTENSITY (EFFECTS)  Modified Mercalli Intensity Scale Measures damage produced by anearthquake  Useful for:  historic quakes  earthquake engineering  pin-pointing damaged localities Guiseppe Mercalli

What affects intensity?  Amount of energy released in the earthquake  Distance from the epicenter  Type of bedrock  Population density  Building construction 1989 Loma Prieta Earthquake USGS

MEASURING EARTHQUAKES MAGNITUDE (Wave Amplitude)  Richter Scale – based on largest amplitude of a seismic wave from seismograph during an earthquake  An increase by 1 in magnitude equals 10x magnitude equals 10x increase in amplitude increase in amplitude  Measure of the amount of energy released  Energy released increases 32 x’s for each unit Charles Richter

Earthquake Energy Equivalents Education and Outreach IRIS Consortium:

MEASURING EARTHQUAKES MOMENT MAGNITUDE  More accurate than Richter Scale  Estimates total amount of energy released  Takes into account several factors  Displacement along fault  Area of ruptured surface  Strength of underlying rock  More precisely measures large earthquakes, similar magnitudes earthquakes, similar magnitudes as Richter for smaller quakes as Richter for smaller quakes  Can be verified by field studies of fault displacement measurements fault displacement measurements

EARTHQUAKE HAZARDS  Ground shaking  Liquefaction  Fire  Subsidence & uplift  Landslides & avalanches  Tsunamis Mexico City Earthquake, September 19, 1985 USGS

Earthquake Hazard GROUNDSHAKING  Strain accumulation  One side of the fault is moving in opposition to the other side of the fault  Result: ground cracks and structures collapse Mexico City Earthquake, 1985 Oklahoma University

Ground Shaking and Cracking San Francisco Earthquake 1906 G.K. Gilbert

Landers, CA M Earthquake

Kobe, Japan  January 17, 1995  6.9M Press & Siever

Kobe, Japan  Expressway fell on it’s side  6308 killed Press & Siever

Tohoku, Japan March 11,2011 Magnitude 9.0  401 aftershocks  4 foreshocks  18,000+ killed

Ground Shaking Material Amplification  Surface waves are relatively small in solid crystalline bedrock  Surface waves amplify (increase) in poorly consolidated sediments Prentice Hall

Mexico City Earthquake, 1985 City built on lake sediments that amplified seismic waves

1985 Mexico City Earthquake - M 8.1

Earthquake Hazard LIQUEFACTION  Sand grains saturated with water shake  Sand grains are detached  Sand is unable to support overlying weight of buildings Niigata, Japan 1964 Karl V. Steinbrugge

LIQUEFACTION Marina District in San Francisco Loma Prieta Earthquake – 1989 M 7.1

Nimitz Freeway 1989 Loma Prieta Earthquake – M 7.1 Dennis Laduzinski

Earthquake Hazard FIRE Causes:  Gas mains break  Gas stoves, water heaters, etc. in homes  Inadequate water supply  Firefighters can’t reach fire  Blasting sometimes used to create a fire break Kobe, Japan 1995San Franscico, 1906

Fire San Francisco Earthquake 1906  April 18, 1906  5:15 am  Shaking lasted about 1 minute  killed  8.3M estimated  $400 million in damages (Image © Archive Photos)

Earthquake Hazard SUBSIDENCE & UPLIFT Alaska Earthquake 1964 Prince William Sound Fault Scarp of 16 feet USGS

Earthquake Hazard LANDSLIDES & AVALANCHES  Unstable material shaken loose  Rock, sediment or ice  Steep slopes 2002 Alaska Earthquake

Yungay, Peru  8 M earthquake  20,000 killed in Yungay  50,000 more killed elsewhere Overlandy.com about 2003

Earthquake Hazard TSUNAMIS Seismic Sea Wave Causes:  Submarine landslide  Fault displacement  Volcanic eruption TASA

Tsunami

Tsunamis in the Pacific

Hilo, Hawaii April 1, 1946 – 159 Deaths NOAA

Indian Ocean Tsunami Natl. Inst. of Advanced Industrial Science & Technology NOAA

Indian Ocean Tsunami Dec. 26, 2004 Banda Aceh, Sumatra Reuters Patong Beach, Phuket

Banda Aceh, 2004 Tsunami

Japan, 2011 Tsunami videovideo2 videovideo2 video1

HAZARD ASSESSMENT  Develop understanding of the earthquake source  Determine earthquake potential  Predict effects of earthquakes  Apply research results Coalinga, CA 1983 Earthquake USGS

Shaking Hazard Map

World Seismic Hazard Press & Siever

San Andreas Fault south of San Francisco R.E. Wallace, USGS

EARTHQUAKE PREDICTION (when) verses EARTHQUAKE FORCASTING (where)

Earthquake Studies  Tilt of rocks  Swarms of micro- earthquakes  Groundwater changes  Radio Waves  Creep verses locked faults  Foreshocks/Aftershocks  Animal behavior  and more... Parkfield, CA - SAFOD San Andreas Fault Observatory at Depth USGS

Parkfield, CA Earthquake Capitol of the World 6M earthquakes - 21 year average (4.5 M) 1994 (5 M) 2004!

Earthquake Probability San Andreas Fault

Chinese Predict Haicheng Earthquake February 1975 Prediction based on:  Foreshocks  Many large foreshocks before main event  Animal Behavior  Snakes came out of hibernation  Rats scurried around  Large farm animals behaved differently near epicenter Collapsed Factory China Virtual Earthquake Museum

Chinese fail to predict Tangshan Earthquake July 28, 1976  2 nd most devastating earthquake in history (worst was also in China 1556, 830,000 died)  8.2 M  750,000 died  No foreshock events ChinaStock