The Next Bay Area Earthquake

What to expectWhere? When? How Large?Dr. John Boatwright, Bay Area Earthquake Alliance Co-Chair

Co-Regional Coordinator for Northern California US Geological Survey

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North AmericanNorth Americanplateplate

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40 mm/yr Farallons-Sierra Nevada

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What is the History of Large Earthquakes in the

Bay Area?• 1989 Loma Prieta (M6.9)

• 1906 San Francisco (M7.8)

• 1868 Hayward (M6.8)

• 1838 Peninsula (M7?)

• Paleoseismic Earthquakes (pre-1776) identified

by trenching active faults

“We need to correct our style of architecture … to work a savings of untold sums of money in the future” - San Jose Mercury News October 29, 1868

Hayward Earthquake

1868

San Francisco

1906

Cum

ulat

ive

M0,

dyn

e-cm

Moment Accumulation in the SF Bay Region

1989

Loma Prieta

Bay Area Earthquake History

1600-2000 A.D.

In the next 30 years, there is a 63% prob-ability, nearly a 2/3rds chance, of an M6.7 or larger earthquake in the greater Bay Area. Hazard is highest in the East Bay due to the larger number of faults there, including the Hayward fault.(UCERF2 Report, 2007)

2007-2036

21%

31%

3%

1%

3%63%

6%

7%

11%

M ≥ 6.7

Hazard is highest in the East Bay due to the larger number of faults including theHayward Fault.

1868 Hayward1868 HaywardEarthquakeEarthquake

Near-Field MMI Near-Field MMI Intensities areIntensities are strong strong from Sanfrom SanLeandro south Leandro south through Hayward through Hayward towards Alvaradotowards Alvarado(MMI 8-9 & 9)(MMI 8-9 & 9)

But they appearBut they appear moderatemoderate in both in both Oakland and Oakland and MilpitasMilpitas(MMI 7-8 & 8)(MMI 7-8 & 8)

38°

-122.5°

37.5°

-122°

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Hayward Fault Earthquake:The Infrastructure Earthquake

QuickTime™ and aH.264 decompressor

are needed to see this picture.

Animation of Shaking from a M7.0 on the Hayward FaultFremont Epicenter

http://earthquake.usgs.gov/regional/nca/simulations/hayward/

QuickTime™ and aH.264 decompressor

are needed to see this picture.

Losses by county - M7.0 scenario

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Solano

Sonoma

Santa Clara

Santa MateoSan

Francisco

Marin

Contra Costa

Alameda

$0 $40B $80 $100

Economic Loss ($Billions)

What can happen in the urban neighborhoods of the Bay Area in next large earthquake?

• Soft-Story Damage & Failures

• Fire Following Earthquake

Soft-Story Buildings

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soft-story retrofits in San Francisco are still voluntary

rather than mandatory

This photo shows the vulnerability

that the Loma Prieta earthquake exposed

We Were Very Fortunate in 1989

Marina fireTo Have Favorable Fire Conditions

38°

37.5°

37°

123° 122° 121°

google: cisn shakemap nchttp://www.cisn.org/shakemap/nc/shake/