Here is the straight dope on earthquakes…


  • An earthquake is a sudden slipping or movement of a portion of the Earth’s crust or plates, caused by a sudden release of stresses. Earthquake epicenters are usually less than 25 miles below the Earth’s surface and are accompanied and followed by a series of vibrations. Earthquakes can occur anywhere and without any obvious warning.

Earthquakes are such a risk because shaking ground can:

  • Cause buildings to move off of their foundations or collapse.
  • Damage utilities, communications, structures, and roads.
  • Severely compromise emergency services.
  • Cause fires and explosions.
  • Cause structural instability, such as dam failures that can trigger flash floods.
  • Earthquakes can also trigger landslides and avalanches or tsunamis. After an earthquake, it is important to listen for emergency instructions.
  • Together, all of these types of damage threaten lives, property, and the environment.
  • There is no seasonal or yearly cycle of earthquake occurrence; earthquakes can happen at any time. Major earthquakes appear to occur in cycles of between 50 and 275 years.
  • An earthquake may last for seconds or minutes, while aftershocks may occur for months after the main earthquake.

The Richter Scale

  • Earthquakes are classified, based on the Richter Scale, as:
  • Small: 5.0-5.9
  • Moderate: 6.0-6.9
  • Major: 7.0-7.9
  • Great: 8.0 or greater
  • The Richter Scale measures earth movement caused by an earthquake. The Richter Scale has a logarithmic base, so each increment on the scale is multiplied by a factor of 10.
  • For example, an earthquake of magnitude 8.6 would not be twice as violent as one of 4.3, but rather would be 10,000 times worse. The 10 fold is in regard to amplitude. The actual energy released by an earthquake increases 31 times for each whole number increment.

What is their likelihood?

  • Twenty-six urban areas in all parts of the United States are identified as carrying significant risk of earthquake:
  • The Western United States, particularly along the San Andreas Fault in California, the Cascadia Subduction Zone in western Oregon and Washington, and up the Alaskan coast
  • The New Madrid Fault Zone in Missouri
  • A few pockets on the east coast, including coastal South Carolina and New England


  • More than 75 million Americans in 39 states face significant risk from earthquakes.
  • California’s 17 million people face the highest risk, followed by the residents of western Washington State.
  • Four million people are within the destructive reaches of the New Madrid Fault.

Why do some smaller quakes cause more injuries than larger ones?

  • Location: An earthquake that hits in a populated area is more likely to do damage than one that hits an unpopulated area or the middle of the ocean.
  • Magnitude: The greater the energy released, the more the damage.
  • Depth: In general, deeper earthquakes are less damaging because their energy dissipates before it reaches the surface.
  • Distance from the epicenter: The epicenter is the point at the surface right above where the earthquake originates and is usually the place where the earthquake’s intensity is the greatest
  • Local geologic conditions: The nature of the ground at the surface of an earthquake can have a profound influence on the level of damage.
  • Secondary effects: Earthquakes can trigger landslides, fires, floods or tsunamis.  (Or in the case of Northridge, mold and heart attacks)
  • Architecture: Even the strongest buildings may not survive a bad earthquake, but architecture plays a huge role in what and who survives a quake.
  • Population Density: The more people, the more chance for injury and casualty.
  • Emergency Response: How many emergency responders to population? 3,000 LAFD to 4,000,000 people in LA and only 1,000 on in a shift. That is 4,000 people per emergency worker. 
  • Lack of Preparation and Education: “it’s never going to happen to us.” Ignorance kills as much as an earthquake.

What kind of scenario are we looking at after a major earthquake?

  • No power for days, weeks or longer
  • Cell phones and internet will be out
  • All major utilities will be impacted including water, sewer and gas
  • Freeway collapse
  • Landslides and fires
  • Compromised or unavailable emergency services

What this means is that in a MAJOR quake (i.e. “The Big One”) it is extremely likely that you will have no power, water, sewer, communications, 911 and with no help on it’s way. In a major event the LAFD will spend the first two to three days simply making an assessment of the city do decide where to direct resources. You will not be able to purchase goods without cash and even then items will be at a premium if they exist at all. Food stores only have a three day supply and navigating the city will be difficult or in some cases impossible. You may have to leave your home due to damage, fire or flooding. Though the population of Los Angeles is just under 4 Million people, the Greater Los Angeles area is 18.7 Million, which means available resources will quickly vanish.  Close to 60 percent of Americans are wholly unprepared for a disaster of any kind.