Faults and Earthquakes

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Faults and Earthquakes
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Some Important Earthquakes

• 1755 - Lisbon, Portugal
• Killed 70,000, Raised Waves in Lakes all over
  Europe
• First Scientifically Studied Earthquake
• 1811-1812 - New Madrid, Missouri
• Felt over 2/3 of the U.S.
• Few Casualties
• 1886 - Charleston, South Carolina
• Felt All over East Coast, Killed Several Hundred.
  
• First Widely-known U.S. Earthquake

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Some Important Earthquakes

• 1906 - San Francisco
• Killed 500 (later studies, possibly 2,500)
• First Revealed Importance of Faults
• 1923 Tokyo - Killed 140,000 in firestorm
• 1964 - Alaska
• Killed about 200
• Wrecked Anchorage.
• Tsunamis on West Coast

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Some Important Earthquakes

• 1976 - Tangshan, China
• Hit an Urban Area of Ten Million People
• Killed 650,000
• 2004 Indian Ocean
• 300,000 killed
• Worst Tsunami Disaster in History
• 2010 Haiti
• Not very strong but 200,000 killed

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Seismic Waves
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Elastic Rebound
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Epicenter and Focus

• Focus
• Location within the earth where fault rupture
  actually occurs
• Epicenter
• Location on the surface above the focus

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Types of Faults

• Faults Are Classified According to the Kind of
  Motion That Occurs on Them
• Joints - No Movement
• Strike-Slip - Horizontal Motion
• Dip-Slip - Vertical Motion

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Joints

• Aseismic No Earthquake Hazard
• Environmentally Important Because They Influence
• Rock Strength
• Landslides and Slope Failure
• Ground Water Movement

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Joints, Utah
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Joints, Marathon County
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Joints, Door County
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Strike-Slip Fault Left Lateral
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Strike-Slip Fault Right Lateral
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San Andreas Fault, California
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Crystal Springs Dam
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Fault Gouge, San Andreas Fault
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San Andreas Fault, San Bernardino, California
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San Andreas Fault, California
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San Andreas Fault, Cajon Pass, California
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Hayward Fault, California
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Fault Creep, Hayward Fault, California
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Fault Creep, Hayward Fault, California
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Hollister, California
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Hollister, California
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Hollister, California
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Mission Impossible
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1812 Earthquake Damage
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Carizzo Plain, California
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Carizzo Plain, California
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Carizzo Plain, California
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Offset Stream, California
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Tsunami Alert!
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Rapid Uplift, Sierra Nevada
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California Earthquakes Then
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And Now
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Dip-Slip Faults

• Normal Faults Extension
• Reverse Faults Compression
• Reverse Faults are often called Thrust Faults

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Dip-Slip Fault - Normal
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Fault Surface, Provo, Utah
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Normal Fault, California
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Moab Fault, Utah
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Front Range Fault, Colorado
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Sierra Nevada, Manzanar, California
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Owens Valley, California
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Owens Valley, California
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Horsts and Grabens, California
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Horsts and Grabens, California
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Soft-Sediment Graben
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Graben, Wasatch Fault, Utah
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Horst, Nevada
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1950 Fault Rupture, Nevada
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1950 Fault Rupture, Nevada
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1950 Fault Rupture, Nevada
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Dip-Slip Fault - Reverse
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Thrust Fault, Antarctica
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Sheared Rock on Thrust Fault, Antarctica
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Thrust Faults, Appalachians
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Thrust Fault, Tennessee
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Thrust Fault Structures
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Mountain Scenery, Tennessee
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Window, Tennessee
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Floor of Window, Tennessee
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Chief Mountain, Montana
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Above the Thrust Fault
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Below the Thrust Fault
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Ice-Free Corridor
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Thrust Faults in Snow
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Moine Thrust, Scotland
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Moine Thrust, Scotland
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Melange, Newfoundland
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Melange, Newfoundland
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Major Hazards of Earthquakes

• Building Collapse
• Landslides
• Fire
• Tsunamis (Not Tidal Waves!)

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Safest Most Dangerous Buildings

• Small, Wood-frame House - Safest
• Steel-Frame
• Reinforced Concrete
• Unreinforced Masonry
• Adobe - Most Dangerous

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Not the Best Place to Build?
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Construction, Turkey
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Construction, Turkey
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Construction, Turkey
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Construction, Bosnia
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Tile Roof, Costa Rica
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Tile Roof, Costa Rica
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Adobe Buttresses, Texas
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Rebar in Freeway, California
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Earthquake Bolts, Charleston SC
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Tsunamis

• Probably Caused by Submarine Landslides
• Travel about 400 M.p.h.
• Pass Unnoticed at Sea, Cause Damage on Shore
• Warning Network Around Pacific Can Forecast
  Arrival
• 2004 disaster creates push for global system
• Whether or Not Damage Occurs Depends on
• Direction of Travel
• Harbor Shape
• Bottom
• Tide Weather

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Tsunami Warning Sign
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Fire

• Tokyo, 1923
• San Francisco, 1906
• San Francisco, 1989
• Hazards
• Broken water mains
• Broken gas lines
• Electrical shorts
• Broken or overturned fuel tanks
• Streets blocked

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Firestorms

• Old Growth Forests (Peshtigo, 1871)
• Pre-WWII Cities (Dresden, Hamburg, Tokyo)
• Not second growth or modern cities
• Requires several pounds of combustible material
  per square foot
• A true firestorm is a mesocyclone
• Term often used loosely and inaccurately

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Magnitude and Intensity

• Intensity
• How Strong Earthquake Feels to Observer
• Magnitude
• Related to Energy Release
• Determined from Seismic Records
• Rough correlation between the two for shallow
  earthquakes

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Intensity

• How Strong Earthquake Feels to Observer
• Depends On
• Distance to Quake
• Geology
• Type of Building
• Observer!
• Varies from Place to Place
• Mercalli Scale- 1 to 12

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Mercalli Scale

• I. Only the most sensitive people notice any
  movement.
• II. A few people notice movement if they are at
  rest or on the upper floors of tall buildings.
• III. Many people indoors feel movement. Hanging
  objects swing back and forth. People outdoors
  might not notice anything.
• IV. Most people indoors feel movement. Dishes,
  windows, and doors rattle. A few people outdoors
  may feel movement. Parked cars rock.
• V. Almost everyone feels movement. Sleeping
  people are awakened. Small objects move or are
  turned over. Trees might shake. Liquids might
  spill out of open containers.
• VI. Everyone feels movement. People have trouble
  walking. Objects fall from shelves. Pictures fall
  off walls. Furniture moves. Plaster in walls
  might crack. No major structural damage.

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Mercalli Scale

• VII. People have difficulty standing. Drivers
  feel their cars shaking. Damage is slight to
  moderate in well-built buildings considerable in
  poorly built buildings.
• VIII. Drivers have trouble steering. Houses might
  shift on their foundations. Towers and chimneys
  might twist and fall. Well-built buildings suffer
  slight damage. Poorly built structures suffer
  severe damage.
• IX. Well-built buildings suffer considerable
  damage. Houses move off their foundations. Some
  underground pipes are broken. The ground cracks.
  Reservoirs suffer serious damage.
• X. Most buildings and their foundations are
  destroyed. Some bridges are destroyed. Dams are
  seriously damaged. Large landslides occur.
  Railroad tracks are bent slightly.
• XI. Most buildings collapse. Underground
  pipelines are destroyed. Railroad tracks are
  badly bent.
• XII. Almost everything is destroyed. Objects are
  thrown into the air. The ground moves in waves or
  ripples.

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Isoseismals from the 1906 San Francisco
Earthquake
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Intensity and Geology in San Francisco, 1906
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Intensity and Bedrock Depth in San Francisco,
1906
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Candlestick Park
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California Faults
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San Francisco and New Madrid Compared
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New Madrid, Missouri
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New Madrid, Missouri
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1811-12 Sand Blows, New Madrid, Missouri
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1811-12 Sand Blow, New Madrid, Missouri
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1811-12 Subsidence, New Madrid, Missouri
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Magnitude - Determined from Seismic Records

• Richter Scale
• Related to Energy Release
• Exponential
• No Upper or Lower Bounds
• Largest Quakes about Mag. 8.7

• Magnitude-Energy Relation
• 4 - 1
• 5 - 30
• 6 - 900
• 1 Megaton about 7
• 7 - 27,000
• 8 - 810,000

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Magnitude and Energy
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Magnitude and Energy
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Seismic - Moment Magnitude

• A Seismograph Measures Ground Motion at One
  Instant But --
• A Really Great Earthquake Lasts Minutes
• Releases Energy over Hundreds of Kilometers
• Need to Sum Energy of Entire Record
• Modifies Richter Scale, doesn't replace it
• Adds about 1 Mag. To 8 Quakes

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Are Earthquakes Getting More Frequent?
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Earthquake Fatalities Since 1800
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Earthquake Fatalities Since 1800
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Earthquake Fatalities

• The dozen or so events with more than 100,000
  fatalities account for a large fraction of the
  total.
• 2.9 million earthquake fatalities since 1900
• 3.8 million since 1800
• 7.7 million since 1500
• Known total for all recorded earthquakes is
  around 12.5 million.

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Strategies of Earthquake Prediction

• Lengthen Historical Data Base
• Historical Records
• Paleoseismology
• Short-term Prediction
• Precursors

• Long-term Prediction
• Seismic Gaps
• Risk Levels
• Modeling
• Dilatancy - Diffusion
• Stick - Slip
• Asperities
• Crack Propagation

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Seismic Gaps
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A Prediction Strategy That Just Didnt
WorkCienega Winery, Hollister, CA
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Lidar Mapping
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900 AD Fault Scarp, Washington
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Trenched Fault, Washington
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Tacoma Fault and Glacial Troughs
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Earthquakes and Plate Margins
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Intraplate Earthquake Analogy
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US Seismic Risk
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