San Francisco Bay Area Earthquakes: The Hayward and San Andreas Faults are probably the most studied earthquake faults in the world, so a lot is known about them. Their geology is why we even think of retrofitting a home.
The Greatest Natural Disaster in the History of the United States is Coming Soon.
Here is the graphic history of earthquakes on the Hayward fault. It has an average repeat cycle of 140 years. As of 2020, it has been 151 years since the last big earthquake in 1868. In other words, in 11 more years, we will have exceeded the historic maximum span of 160 years (U.C. Berkeley Seismological Laboratory).
Bay Area Earthquakes: Hayward Fault Damage Will Be Devastating
According to the Association of Bay Area Governments, the Hayward Fault will cause $165 billion in damage when it ruptures. The chart below should give you some perspective on how much devastation this is compared to other large earthquakes.
The USGS also has a webpage that analyzes what will happen if a 7.0 earthquake has its epicenter in Oakland or Fremont.
This BBC video explores what a 9.0 quake would do to the west coast.
According to government statistics, an even larger earthquake on the entire Hayward fault plus the already linked Calaveras Fault would reach magnitude 7.3. Over 155,000 housing units will suffer enough damage to become uninhabitable and 350,000 people will be displaced. The earthquake will cause $90.4 billion in damage to residential buildings and $96.4 billion in commercial buildings. Page 75 of the online version of The Coming Bay Area Earthquake: 2010 Update of Scenario for a Magnitude 7.0 Earthquake on the Hayward Fault published by the Earthquake Engineering Research Institute describes the situation vividly. For a 12-minute video concerning the Hayward Fault, see the KQED documentary Predictable Peril.
Ordinary Houses will Sustain Significant Damage
On page 10 of Seismic Behavior of Level and Stepped Cripple Walls by Y. H. Chai, it states, “More than half of the $40 billion dollar property losses in the Northridge Earthquake were due to failures of wood frame construction, primarily as a result of the damage or collapse of residential, single-family homes.” Damage from the Hayward Fault will greatly exceed this.
Practically every house is the Bay Area is being threatened. We have identified 4 common types of houses and have written web pages and made videos to show you how to retrofit them. This includes Cripple Wall Retrofits, No Cripple Wall Retrofits, Retrofits of Homes with Living Area above a Garage, and Hillside Home Retrofits.
More Bay Area Earthquakes: The Devastating Potential of the Cascadia and San Andreas Fault Lines
The New Yorker published an article, “The Really Big One,” which warns that the Cascadia Fault is even more dangerous than the Hayward Fault. The author Kathryn Schultz writes “When the next very big earthquake hits, the northwest edge of the continent, from California to Canada and the continental shelf to the Cascades, will drop by as much as six feet and rebound thirty to a hundred feet to the west . . . To see the full scale of the devastation when that tsunami recedes, you would need to be in the international space station.” FEMA conservatively anticipates a death toll of 13,000.
Here is a shorter eye-opening 7-minute TV clip on the Cascadia Fault. This fault regularly generates 9.0 temblors similar to the 2004 Sumatra earthquake and tsunami that killed over 227,000 people in Indonesia and India. The similar magnitude 2011 Tohoku 9.0 earthquake that caused the Fukushima nuclear disaster is discussed in this 3-minute video.
Below is a 50-minute BBC documentary on the Cascadia Fault which triggers the San Andreas Fault 75% of the time when it ruptures. This in turn can cause the Hayward Fault to rupture.
Fascinating BBC Documentary on the Cascadia Fault
CBS News did a short but excellent documentary on the huge impact a rupture of the Cascadia Fault will have on our country.
How Does Ground Movement Cause Damage?
When the ground accelerates, the house and foundation go with it. When the ground stops suddenly the house wants to keep on going- and slides off the foundation. It is similar to riding in the back of a pick-up truck which accelerates very quickly and stops suddenly. When it stops, your body moves as it is pushed forward. A retrofit prevents this kind of movement.