Northridge Earthquake

Some Numbers

• Richter rating 6.7,
• 72 deaths,
• About 12,000 injuries,
• About 8,000 damaged houses,
• About 114,000 damaged structures,
• About $20,000,000,000 damage,
• Happened on a previously unknown fault.
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Blind thrust fault

• Northridge happened on a blind thrust fault.
• Thrust faults are transform faults that rupture upwards rather than horizontally.
• Blind thrust faults are thrust faults that stop rupturing before reaching the surface.
  • They are very difficult to detect.
  • Northridge originated 17 km below surface.
  • Rupturing continued for 8 seconds.

History of Seismic Activity

• Since 1769, 37
• 12 recorded earthquakes, Richter 5.0+, within 50 miles of L.A.
• 25 recorded earthquakes, Richter 6.0+, within 160 miles of L.A.
• June 6, 1992: Mojave Desert. Richter 7.3, $90 million damage.
• October 1, 1989: Whittier Narrows, Richter 5.9, $358 million damage.

Damage

• About 114,000 damaged structures,
• Utilities cut off for days, weeks, or months,
• Major damage to transportation routes
• Four major Southern California freeways (I-5, SR-14, I-10, and SR-118) were severely damaged,
• Within hours of the earthquake, contractors were out, working on managing and repairing the damage.

Emergency Response

• They knew what to do (history of seismic activity),
• They knew how to act (history of emergencies),
• Firefighters were able to mobilize and limit damage from fire,
• Police maintained order and prevented a panic.
• Communication systems were damaged, limiting communication between organizations.

Non-local Response

• Governor’s Office for Emergency Services mobilized the National Guard to provide aid for earthquake victims.
• Office for Emergency Services coordinated the newly established (at the time) Standardized Emergency Management System, which was a multi-agency system of dealing with emergencies.
  • ex: Department of Forestry and Fire Protection sent 600 personnel members to the region to assist recovery and damage assessment.

Local Response

• The United States government declared the Northridge earthquake a national disaster.
• $11,000,000,000 federal assistance was sent to the Los Angeles and Ventura counties.
• The Federal Emergency Management System (FEMA) sent personnel in to assist in recovery.
• National Earthquake Hazards Reduction Program (NEHRP) agencies were put in charge of helping in long-term recovery. (FEMA, USGS, National Science Foundation, National Institute of Standards and Technology).

Effect on Insurance Industry

• Northridge caused about $12.5 billion in insured damage.
• California law states organizations selling residential property insurance must offer earthquake coverage.
• Insurance industry didn’t want to lose more money, so they limited their offers, or stopped offering home insurance completely

California Policy Response

• California Legislature took two steps:
  • They created the “mini policy”: a standard for the minimum protection that must be offered as earthquake insurance.
  • They created the California Earthquake Authority (CEA), a publicly managed, privately funded organization that provides earthquake insurance coverage to members. It is non-mandatory.

Conclusion

• Northridge was devastating (deaths, injuries, damage),
  Response was quick and effective (both locally and state-wide),
  It caused legislation regarding earthquake insurance to be revised and rewritten to better protect insurance buyers and sellers.