1
EarthquakesGeology 8L
2 April 2007Lecture Slides Modified from USGS Presentation
Lisa WaldUSGS Pasadena
U.S. Department of the InteriorU.S. Geological Survey
USGS Earthquake Hazards Program
Earthquakes 101 (EQ101)
Global Distribution of Earthquakes
2
Lisa WaldUSGS Pasadena
U.S. Department of the InteriorU.S. Geological Survey
USGS Earthquake Hazards Program
Plate Tectonics
Plate Boundaries
3
Three Types of Faults
Strike-SlipThrust
Normal
Strike-slip Fault Example
Strike-slip Fault Example
1906 San Francisco Earthquake
4
Normal Fault Example
Dixie Valley-Fairview Peaks, Nevada earthquakeDecember 16, 1954
Thrust Fault Example
Thrust Fault Example
5
Total Slip in the M7.3 Landers Earthquake
Rupture on a Fault
MDepth
Into the
earth
Surface of the earth
Distance along the fault plane100 km (60 miles)
Slip on an earthquake fault
START
6
Slip on an earthquake faultSecond 2.0
Slip on an earthquake faultSecond 4.0
Slip on an earthquake faultSecond 6.0
7
Slip on an earthquake faultSecond 8.0
Slip on an earthquake faultSecond 10.0
Slip on an earthquake faultSecond 12.0
8
Slip on an earthquake faultSecond 14.0
Slip on an earthquake faultSecond 16.0
Slip on an earthquake faultSecond 18.0
9
Slip on an earthquake faultSecond 20.0
Slip on an earthquake faultSecond 22.0
Slip on an earthquake faultSecond 24.0
10
Bigger Faults Make Bigger Earthquakes
1
10
100
1000
5.5 6 6.5 7 7.5Magnitude
Kilo
met
ers
8
Bigger 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?
• Magnitude– More energy released
• Distance– Shaking decays with distance
• Local soils– amplify the shaking
11
Earthquake Effects - Ground Shaking
Northridge, CA 1994
Earthquake Effects -Ground Shaking
Northridge, CA 1994
Earthquake Effects - Ground Shaking
KGO-TV News ABC-7
Loma Prieta, CA 1989
12
Earthquake Effects - Ground Shaking
Kobe, Japan 1995
Earthquake Effects - Ground Shaking
Kobe, Japan 1995
Earthquake Effects - Surface Faulting
Landers, CA 1992
13
Earthquake Effects - Liquefaction
Source: National Geophysical Data Center
Niigata, Japan 1964
Earthquake Effects - Landslides
Turnnagin Heights,Alaska,1964
Source: National Geophysical Data Center
Earthquake Effects - Fires
KGO-TV News ABC-7
Loma Prieta, CA 1989
14
Earthquake Effects - Tsunamis
Photograph Credit: Henry Helbush. Source: National Geophysical Data Center
1957 Aleutian Tsunami
Seismic Waves
Earthquake Magnitude
M5
M6
M7
15
Earthquake Location
The San Andreas Fault
Pacific-North American Plate Boundary
16
Shaking Hazard in Southern California
Real-time Earthquake Information
Did You Feel It?
CommunityInternetIntensityMaps
17
U.S. Department of the InteriorU.S. Geological Survey
USGS Earthquake Hazards Program
http://pasadena.wr.usgs.gov/http://earthquake.usgs.gov/
Where to go for more information:
