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: