earthquakes by mr. d and some slides taken from the usgs
TRANSCRIPT
Earthquakes By Mr. D and some slides taken from the USGS
Earthquakes usually occur on faults caused by the subduction of two plates
Lisa WaldUSGS Pasadena
U.S. Department of the InteriorU.S. Geological Survey
USGS Earthquake Hazards Program
Plate Tectonics
Plate Boundaries
Three Types of Faults
Strike-SlipThrust
Normal
Strike-slip Fault Example
Normal Fault Example
Dixie Valley-Fairview Peaks, Nevada earthquakeDecember 16, 1954
Thrust Fault Example
Thrust Fault Example
Bigger Faults Make Bigger EarthquakesBigger Faults Make Bigger Earthquakes
1
10
100
1000
5.5 6 6.5 7 7.5Magnitude
Kilo
me
ters
8
Bigger Earthquakes Last a Longer TimeBigger Earthquakes Last a Longer Time
1
10
100
5.5 6 6.5 7 7.5 8
Magnitude
Sec
onds
What Controls the Level of Shaking?What Controls the Level of Shaking?
• Magnitude– More energy released
• Distance– Shaking decays with distance
• Local soils– amplify the shaking
Is there such a thing as “Earthquake Weather”???
Earthquake Effects - Ground Shaking
Northridge, CA 1994
Earthquake Effects - Ground Shaking
KGO-TV News ABC-7
Loma Prieta, CA 1989
Earthquake Effects - Surface Faulting
Landers, CA 1992
Earthquake Effects - Landslides
Turnagain Heights, Alaska,1964 (upper left inset);Santa Cruz Mtns, California , 1989
Source: National Geophysical Data Center
Earthquake Effects - Fires
KGO-TV News ABC-7
Loma Prieta, CA 1989
Earthquake Effects - Tsunamis
Photograph Credit: Henry Helbush. Source: National Geophysical Data Center
2011 Tsunami in Japan
Seismic Waves
Richter magnitude scale
• One way we measure magnitude.
• Developed in 1935 by Charles Richter in partnership with Beno Gutenberg, both of the California Institute of Technology.
• An earthquake that measures 5.0 on the Richter scale has a shaking amplitude 10 times larger than one that measures 4.0.
Earthquake Magnitude
Earthquake Magnitude ScaleMagnitude Earthquake Effects Estimated
• 2.5 or less: Usually not felt, but can be recorded by seismograph (frequently occurs in CA).
• 2.5 to 5.4: Often felt, but only causes minor damage. • 5.5 to 6.0: Slight damage to buildings and other structures.• 6.1 to 6.9May cause a lot of damage in very populated
areas.• 7.0 to 7.9: Major earthquake. Serious damage.20• 8.0 or greater: Great earthquake. Can totally destroy
communities near the epicenter.
EPICENTER
• the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates.
Earthquake Location
The San Andreas Fault
Pacific-North American Plate Boundary
Will California eventually fall into the ocean???
Why not?
• The motion between the pacific and the north American plates beneath us is mostly horizontal. That is, the Pacific plate is moving "up" the coast, not away from the North American plate, at a rate of dozens of millimeters per year.
• So in several million years, residents of San Francisco will see the L.A. skyline out their windows.
Faultsof SouthernCalifornia
Source: SCEC Data Center
Shaking Hazard in Southern California
Real-time Earthquake Information
Any Questions?
• Remember you will have a test on this- so ask the questions now before you forget.