u.s. department of the interior u.s. geological survey the earthquake is inevitable: the disaster is...
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U.S. Department of the InteriorU.S. Geological Survey
The Earthquake is Inevitable:The Disaster is Not 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 InteriorU.S. Geological Survey
The Earthquake is Inevitable:The Disaster is Not 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 energyA bigger fault means a bigger earthquake
RuptureSurface
Hypocenter
Hypo-center
Epi-center
Faultplane
Fault
1
10
100
1000
5.5 6 6.5 7 7.5Magnitude
Kilometers
8
Bigger Faults Make Bigger Earthquakes
Shaking = damage potential
ShakeMap
M4.8 Yorba Linda Yorba Linda September 2002September 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 MineOctober 16, 1999M7.1
NorthridgeJanuary 17, 1994M6.7
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
Undamaged Buildings on the fault
1906 San Francisco
Damage at Great Distance
The Bay Bridge
1989 Loma Prieta
The Marina District
SiteEffects
Big earthquakes on big faults
• M7.9 Denali, Alaska• November 3, 2002• 200+ mile long fault
Near people…
Magnitude = Time
• Earthquakes start at hypocenter
• The rupture moves over a surface Duration of earthquake depends on
magnitude
Total Slip in the M7.3 Landers EarthquakeTotal Slip in the M7.3 Landers Earthquake
Distance along the fault plane, 100 km (60 miles)
total length
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: StartSlip on an earthquake fault: Start
Slip on an earthquake fault: Second 2.0Slip on an earthquake fault: Second 2.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 4.0Slip on an earthquake fault: Second 4.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 6.0Slip on an earthquake fault: Second 6.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 8.0Slip on an earthquake fault: Second 8.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 10.0Slip on an earthquake fault: Second 10.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 12.0Slip on an earthquake fault: Second 12.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 14.0Slip on an earthquake fault: Second 14.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 16.0Slip on an earthquake fault: Second 16.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 18.0Slip on an earthquake fault: Second 18.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 20.0Slip on an earthquake fault: Second 20.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 22.0Slip on an earthquake fault: Second 22.0
Depthinto the
earth
Surface of the earth
Distance along the fault plane, 100 km (60 miles)
total length
Slip on an earthquake fault: Second 24.0Slip 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 TimeBigger Earthquakes Last a Longer Time
1
10
100
5.5 6 6.5 7 7.5 8
Magnitude
The Risk in Southern California
• 300+ faults
• One M≥6.7 event per 7 years
The Big Bend
Los Los Angeles Angeles has the has the greatest greatest risk in the risk in the United United StatesStates
The bottom line: Earthquakes happen
Courtesy of California Geological Survey & U. S. Geological SurveyCourtesy 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, Courtesy of Ned Field, USGS, PasadenaUSGS, Pasadena