Archive for the ‘The Hayward fault’ Category

The East Bay Seismic Investigation

12 September 2016

On Friday I got my first look at a seismic survey that will be visualizing the Hayward fault (and the Chabot fault for good measure) this fall. It involves a 15-kilometer line of several hundred seismometers stretching from the San Leandro shoreline to Cull Canyon. A team of geologists from the US Geological Survey and Cal State East Bay will set off 19 small explosions along the line to serve as energy sources, and the seismometers will record the sound waves as they arrive, after traveling through the various layers of the ground. Here’s the line of charges (as usual, click it for the full-size version); the seismic stations are too numerous to bother showing.

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The Hayward fault is the red line, the Chabot fault is the blue line, and I’ve added the lidar swath along the fault between the light-blue lines. The purple line is the little-known Miller Creek fault.

The occasion on Friday was a photo op for the press. The team drilled a 30-foot hole in which charge number 9 will be placed, and a bunch of reporters took a bunch of footage and asked a bunch of questions.

It was a pretty spartan setup. That’s USGS press officers Leslie Gordon waving on the left and Susan Garcia standing on the right. I see them all the time at science meetings.

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It can be very helpful to have press officers around to answer basic questions in press-friendly ways, follow up with extra pictures and so forth.

Here’s the press gathering footage as Joanne Chan of the USGS works the Bobcat.

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Off to the side, the radio and TV people were talking to the chief scientists, Rufus Catchings of the USGS and Luther Strayer of CSUEB. The photogs put their bodies on the line seeking that grab-you image.

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On the table was one of the seismometers — it’s the orange dealie with the prongs. The can holds the power supply and electronics. You stick it firmly into the ground, hook everything up, and stand very still while the shots are fired.

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They’ll do the shots late at night to avoid vehicle vibrations. then they’ll put all the instruments away and fill in the holes. Also, thank all the property owners whose permission was required for this important research. As you can imagine, a boatload of planning had to happen before reaching this stage. The USGS’s National Earthquake Hazards Reduction Program is paying for the project.

I hope to see more of the project as it proceeds and will report back. Meanwhile, see how the press did:

Mercury News

SFGate

KPIX

Marks of the Oakland fault

11 July 2016

Two weeks ago I told you how the city of Hayward inadvertently destroyed a special street corner. It was an informal shrine among geologists because it so clearly displayed the creeping motion of the Hayward fault. I mentioned that Hayward still has plenty of other bent curbs.

So does Oakland. Almost nine years ago in this space, in my very second post, I said that Oakland should take over the Hayward fault and make it our own. With that in mind, here are eight places on the fault that are pretty iconic if you ask me. I present them from south to north.

1. Revere Avenue above Marlow Drive, in Sheffield Village.

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2. Encina Avenue below Castlewood Street, in Oak Knoll.

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3. Ney Avenue near Astor Avenue, just above Fontaine Street.

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4. 39th Avenue at Victor Avenue, in Redwood Heights.

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5. Medau Place near Moraga Avenue, in Montclair Village.

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6. The old firehouse on Moraga Avenue, in Montclair.

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7. Broadway Terrace just west of Route 13, in Upper Rockridge.

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8. In Lake Temescal Regional Park by the park office.

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Here are their locations, shown on the geologic map.

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There are more such places between and beyond these ones, and others in Berkeley and San Leandro too.

An icon lost: The Hayward fault’s Rose/Prospect curb

27 June 2016

Certain places are prized by geologists, especially teachers, for their educational value. Out-of-towners make pilgrimages to them. Sure we all enjoy the Grand Canyon, but real geologists have Siccar Point, Darwin’s outcrop, the Carlin unconformity and other obscure sites on their life lists.

One of those places was right nearby in Hayward, until very recently. At the corner of Rose and Prospect Streets is a corner curb that happened to be built precisely across the Hayward fault, where the steady progress of aseismic creep slowly wrenched it apart.

The best time series of this corner was compiled by Sue Ellen Hirschfeld, a now-retired geology teacher at UC East Bay. It goes back to 1971, and even then there was a sizable offset. Probably the curb was first emplaced in the late 1950s.

It’s a popular site for folks in the know, and there’s at least one Flickr group with lots of photos. The neighbors are probably sick of us, though. I’ve visited it many times, and I sometimes took pictures. This photo is from 2006.

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We’re looking east across the fault. This side is moving northward a few millimeters per year. I came back the next year and took this shot of the “echelon cracks” in the street, with the iconic curb in the corner.

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In 2012 I brought a few enthusiasts to see it; they asked for anonymity but I can show you where they stood.

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A closeup at the time shows that it had a total offset of about 7-1/2 inches, or 20 centimeters, since it was built. The painted arrow at the left shows the offset in the six years since 2006.

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Last week I joined a party of visitors there, and to my dismay the corner has been dismantled. It looks like the plan is to put in a cutout for people with disabilities, which is a good thing and undoubtedly overdue. Still.

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Anyway, I’m here to put the word out: Rose and Prospect is defunct. It is no more. Come back in 20 years. In the meantime, downtown Hayward is full of other examples of bent curbs.

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There’s always the Old City Hall, too, which was built directly on the fault and has long been abandoned. The first time I visited there, maybe 25 years ago, I was looking at the street adjacent to it. As I watched, a little tongue of water emerged in the center of the street and started trickling downhill. Assuming that an old iron water main had just cracked, I found a phone booth and alerted the city. Cleaning up after a creeping fault never ends.