The Dangers of the Hayward, San Andreas, and Cascadia Fault Lines
Since the year 1315, the longest period of time between five major Hayward Fault earthquakes was 160 years. The average was 138 years. October 21, 2008 was the 140th anniversary of the 1868 Hayward Fault earthquake, a magnitude 7. In 2016, we are now at 148 Years! That’s 10 years beyond the average rupture cycle and 12 years before the maximum rupture cycle. In other words we are in trouble.
Below is a graph from the UC Berkeley Seismological Laboratory. The laboratory also publishes a FAQ page that will tell you everything you want to know about our seismic geology. Google Earth will tell you exactly where you live relative to the Hayward Fault and gives a sense of how strong the shaking will be in your house.
If you want to see exactly where your house is in relation to active earthquake faults go the this USGS page. Click on the line “Hayward Fault Map and Tour” , type your address in the search bar and hit enter.
According to government statistics, a quake on the entire Hayward fault would reach magnitude 7.3. It would leave over 155,000 housing units uninhabitable. Over 350,000 people will be displaced. Damage to residential buildings will be $90.4 billion; commercial buildings, another $96 billion. See The Coming Bay Area Earthquake, page 75, by the Earthquake Engineering Research Institute.
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.
The Devastating Potential of the Cascadia and San Earthquake Fault Lines
New studies described in a New Yorker article, “The Really Big One,” warn that the Cascadia Fault is even more dangerous than the Hayward Fault. Kathryn Schultz, the author, was awarded the 2016 Pulitzer Prize for Feature Writing. “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 near 13,000.
Here is an eye-opening, 7-minute TV clip on the Cascadia Subduction Zone. 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 2011 Tohoku 9.0 earthquake that caused the Fukushima nuclear disaster is discussed in this 3-minute video.
This 50 minute long BBC documentary on this earthquake fault also points out that it triggers the San Andreas Fault to rupture 75% of the time, which in turn can cause the Hayward Fault to rupture.
Below is the repeat cycle for the Cascadia Earthquake Fault.
A Hayward Fault Earthquake in Comparison to other Earthquakes
It is expected that when the Hayward Fault ruptures there will be $165 billion in damage. The chart below should give you some perspective on how much devastation this is.
When the shaking starts