California Earthquakes

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California Earthquakes
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Sylmar Earthquake

• About
• When 600 A.M. February 9, 1971
• Where San Fernando Valley
• What Ruptured segment of the San Fernando Fault
  Zone. Magnitude 6.6

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Damage

• 65 people died
• 500 million in damage
• Two hospitals were destroyed
• Freeway Interchange Collapsed

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The Whittier Narrows Earthquake

• About
• When 742 A.M. October 1st, 1987
• Where San Gabriel Valley
• What Slip on a blind thrust fault. Magnitude
  5.9 and 5.3

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Damage

• 3 people died
• 358 million in damage

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Loma Prieta Earthquake

• About
• When 504 P.M. October 17th, 1989
• Where The greater San Francisco Bay Area
• What Reflected seismic waves

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Damage

• 63 people died 3,757 were injured
• 6 billion in damage
• Cypress Street Viaduct
• San Francisco-Oakland Bridge

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Northridge Earthquake

• About
• When 430 A.M. January 17th, 1994
• Where San Fernando Valley
• What Blind Thrust Fault

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Damage

• 51 people died 9,000 were seriously
• Injured
• 44 billion in damage
• 22,000 people left homeless, 25,000 dwellings
  uninhabitable, 9 hospitals lost, 9 parking
  garages collapsed, 9 bridges collapsed, portions
  of 11 major roads closed

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Pictures
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Pictures
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Total Damages and Costs

• Over the past 23 years the costs of these 4
  earthquakes has been a crushing blow for
  California
• The total number of deaths is estimated to be 188
• The total number of injuries is roughly estimated
  to be 8,804
• The estimated costs of damage due to these
  earthquakes is 31,531,000,000

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What Can Be Done?
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Seismic Retrofitting

• Seismic retrofitting is the modification of
  existing structures to make them more resistant
  to seismic activity, ground motion, or soil
  failure due to earthquakes.
• The key elements of seismic retrofitting are the
  levels of modifications and the types of
  modifications

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Levels of Modification

• Public Safety the number one goal is to ensure
  that in the event of an earthquake, a building
  will not fall on the people inside or the people
  passing by. Building will need to be replaced
• Structure Survivability Structure stays for so
  people can exit in the even of an earthquake.
  After the quake it will need extensive repair but
  no need for replacement.
• Primary Structure Undamaged Only cosmetic
  repairs necessary.
• Structure Unaffected Nothing damaged. Used for
  historic structures.

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Types of Modification

• Hybrid Solution Ductile reinforcement and
  joining of rigid plates and beams
• Isolation Required for large masonry buildings.
  The building is separated from the actual
  foundation. The two are joined by steal or
  reinforced concrete beams.
• Dampers Absorb the energy of motion and turn it
  into heat. Helps to reduce the damage of the
  initial shock.
• Reinforcement Adding strength to the original
  structure. The most common form of Seismic
  retrofit.