The Hayward fault by the Oakland Zoo

Most people don’t know this, I think, but the Hayward fault runs right through the Oakland Zoo. I won’t take you there this week; instead let’s look at the residential area just south of the zoo. Here’s the topography from Google Maps, tilted 40 degrees from north to bring out the grain of the land.


The fault runs from the intersection of Golf Links Road and I-580 at the top, between the words “Oakland” and “Zoo,” through the S in “Hood St,” and across the base of the truncated hillside at the bottom. The USGS map of the fault trace shows the specific features of the fault here.


You’ll see things marked in the area just south of the zoo, a length of the fault labeled “G1, sl” and a dotted oval marked “G1, df.” G1 means a geomorphic feature (a landform) of “strongly pronounced” character, the most clear-cut kind of evidence. The first item is a linear scarp and the second is a fault-related depression. They’re somewhat visible in Google Earth if you tilt the view and squint (800 pixels).


If you go there, all this is more apparent. Here’s a view west, toward the bay, down Hood Street across the odd level spot marking the fault. The cross street is Mark Street.


This is looking north up Mark Street toward the zoo. The depression is behind these houses, in their back yards (800 px).


And this is the view toward the Knowland Park hills back up Hood Street from the bend at its west end (800 px). It’s very odd for the steep slope of our foothills to be interrupted this way. Normally a valley like this would be carved by a stream, but none is evident.


In all of Oakland, there are only four places where geomorphic evidence of the fault is ranked “strongly pronounced.” Two of them are now obscured: one was a line of vegetation in Redwood Heights that quarrying has removed, and the other was at Sausal Creek where Park Boulevard crosses the Warren Freeway. The remaining high-grade feature is the valley south of the LDS Temple, which is inaccessible and highly disturbed by landsliding.

So this is Oakland’s clearest trace of what the fault has done to our landscape. To me it looks quite similar to the Jordan Road stretch of the fault.

Even with all that build-up and explanation, you don’t really see much here unless you know what you’re looking at. But this shot I took in 2005 looking south from the zoo parking lot shows the depression pretty well.


Next time you visit the zoo, take a peek. You might also see if the zoo parking lot is showing cracks from fault creep. the last time I looked, they had just repaved everything.

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