U.S. Department of the Interior U.S. Geological Survey The Earthquake is Inevitable: The Disaster is Not

Earthquake Organizations U.S. Geological Survey –Federal agency in Department of Interior Caltech Seismological Laboratory –Private university Southern California Earthquake Center –Consortium of universities & USGS California Geological Survey –State agency in Department of Conservation Office of Emergency Services –State agency in Homeland Security

Today’s speakers Lucy Jones, USGS –Scientist-in-charge for southern California Gary Fuis, USGS –Project chief, Southern California Earthquake Hazards Egill Hauksson, Caltech –Senior Research Associate Ken Hudnut, USGS –Project chief, Southern California Earthquake Hazards Tom Jordan, SCEC –Director, Southern California Earthquake Center

U.S. Department of the Interior U.S. Geological Survey The Earthquake is Inevitable: The Disaster is Not

What is an earthquake?

What is an Earthquake? Sudden slip of one block of rock across another Produces shaking as one of its effects The shaking is what you feel

M5 M6 M7 Magnitude Empirical and arbitrary Defined from ground velocity Each unit means 32 times more energy

M5 M6 M7 Moment Magnitude Depends on: –Fault area –Amount of slip Each unit means 32 times more energy

Every point on the rupture surface releases energy A bigger fault means a bigger earthquake Rupture Surface Hypocenter Hypo- center Epi- center Fault plane Fault

Bigger Faults Make Bigger Earthquakes

Shaking = damage potential ShakeMap Yorba Linda September 2002 M4.8 Yorba Linda September 2002

What Controls the Level of Shaking? Magnitude –More energy released

What Controls the Level of Shaking? Magnitude –More energy released Distance –Shaking decays with distance

Hector Mine October 16, 1999 M7.1 Northridge January 17, 1994 M6.7

What Controls the Level of Shaking? Magnitude –More energy released Distance –Shaking decays with distance Local soils –amplify the shaking

Undamaged Buildings on the fault 1906 San Francisco

Damage at Great Distance The Bay Bridge 1989 Loma Prieta The Marina District

Site Effects

Big earthquakes on big faults M7.9 Denali, Alaska November 3, mile long fault

Near people…

Magnitude = Time Earthquakes start at hypocenter The rupture moves over a surface ñ Duration of earthquake depends on magnitude

Total Slip in the M7.3 Landers Earthquake Distance along the fault plane, 100 km (60 miles) total length

e Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length Slip on an earthquake fault: Start

Slip on an earthquake fault: Second 2.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 4.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 6.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 8.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 10.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 12.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 14.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 16.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 18.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 20.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 22.0 Depth into the earth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Slip on an earthquake fault: Second 24.0 Depth Surface of the earth Distance along the fault plane, 100 km (60 miles) total length

Bigger Earthquakes Last a Longer Time

The Risk in Southern California 300+ faults One M≥6.7 event per 7 years

The Big Bend Los Angeles has the greatest risk in the United States

The bottom line: Earthquakes happen Courtesy of California Geological Survey & U. S. Geological Survey National hazards map

Scenario ShakeMap for M 7.4 Southern San Andreas Rupture Courtesy of Ned Field, USGS, Pasadena