Posted by: walkingthefault | February 22, 2008

A Scary Picture

Nobody, even the most knowlegeable seismologist, knows whether the next earthquake on the Hayward Fault will rip open like a zipper, much less where that scenario would occur. But what we know for certain is that the fault, or at least parts of it, did rip open 140 years ago as the ground to the west of the fault shifted northward by about eight feet. And, remember that 140 years is the average interval for the last five quakes on the fault.

The exact location of the fault is not clearly visible, except to the trained eye. It has taken the digging of a number of trenches to pinpoint exactly where it is. The past 50 years of road construction, building, and landscaping have pretty much wiped out all evidence of it. Take a look at the Google Earth image below. If the red line weren’t there, could you see evidence of the fault? You can’t even see it when walking on the ground. Would anybody in their right mind, knowing what we do today, build a tots’  playground right on top of the fault? Well, take a look at the yellow stick pin in the middle of the image.

That’s the tots’ playground in Codornices Park. I don’t believe the City had the intention of building a kiddies’ playground right on top of an earthquake fault. Probably, the exact location of the fault as shown by the red line became clear long after the playground was built. Let’s take a look at the playground as seen on the ground.

Codornices Tots Playground 

Do you see any sign of an active earthquake fault in that picture? It’s probably right under that sandbox at the bottom of the blue slides. That’s my whole point here. Over the years, the evidence of the fault has been so well disguised that most people, particularly the Moms and Dads with their kids at this playground, have no idea it is there. Same with the people who live in the houses that have been built on the fault. Other than the little shakers we get in Berkeley every few months, with a magnitude of about 4.0 on the Richter Magnitude Scale, there is nothing that’s sufficiently in our face to make us be better prepared.

Don’t forget that the Richter scale is logarithmic. What does that mean? It means that a 5.0 is ten times bigger than the little 4.0 tremors that we often feel, and a 6.0 is ten times bigger than a 5.0, and a 7.0 (which is the minimum that seismologists think will occur soon) is ten times bigger than a 6.0. Ten times ten times ten is 1000, which how much bigger a 7.0 is than the little tremors of the past few months.  But it’s actually worse than that, because it is 31,000 times STRONGER, and it’s the STRENGTH of an earthquake that knocks down buildings. Check this out, and use the USGS Calculator to play with some numbers if you really want a sleepless night.



  1. As I cross the Bay Bridge, I often think that it is the last place I would want to be during an earthquake. Thanks to the information in this post, I can add being in this tot playground with my grandson to that list!

    I look forward to following your travels.

  2. […] your Scary Picture chapter you show that the fault line passes right under the Tots’ Playground in Codornices […]

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