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.


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.


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.


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.


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.


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



Oakland building stones: Verd antique

5 September 2016

California’s state rock is serpentine, and in this blog I’ve picked up, photographed and defended it against detractors. I’ve called serpentine beautiful, adorable, inspiring and more, but I’ve never called it a building stone. However, it can be.

Serpentine in its Sunday best is called verd antique. This closeup is from the iconic I. Magnin building at Broadway and 20th Street.


It resembles a particularly psychedelic marble — a translucent deep jade-green shot with intricate white veins. Petrologically, though, it is nothing like marble and a lot like soapstone. It consists of magnesium-based silicate minerals that are harder and more chemically robust than the calcite or dolomite that makes up marble.

Verd antique is all over downtown Oakland, usually as a subsidiary element at the sidewalk level. The building on 17th Street between Telegraph and Broadway has a particularly large expanse of it.


The Fox Theater building is another notable example. But in this post I want to draw attention to four buildings that do more with verd antique. The I. Magnin building (built 1930) naturally comes first, its entire first story richly faced with this stone.


The Foulkes Building at 419 15th Street (built 1924) has a high facade of verd antique with bronze decorations.


The Moyles-Kappenman building (built 1928), longtime home of Lobe & Velasco Jewelers, has a lovely front of verd antique on 1617 Broadway and an identical one at its other end on 1618 Telegraph.


Finally we have the otherwise undistinguished Wells Fargo building at 2040 Franklin Street, where the public-facing elements (entrances and ATM) are framed in verd antique.


The reason that all of these stones look the same is that for nearly a century a single quarry in Rochester, eastern Vermont, has been supplying the trade with Vermont Verde Antique(tm) stone. It is geologically special because it was squeezed two separate times, like twice-cooked fries, between colliding tectonic plates during the Paleozoic Era. As the supplier’s website puts it, it owes its origin to “highly sheared ultramafic rocks that have been rewelded and metasomatized by the process of serpentinization.” The lighter-colored “Cardiff Marble” serpentine from northern Maryland was once popular but is no longer produced. That stone is found in the White House’s Green Room, the National Archives rotunda and other places in Washington DC.

Verd antique gets its name from the Italian verde antico, “ancient green.” It was popular in Byzantine architecture. Oakland has a few pieces of European-style, brecciated verd antique to be seen here and there.

The stone industry considers verd antique a type of marble (it’s metamorphic and takes a polish) and follows ASTM standards for its manufacture, but verd antique is really its own beast.


You can’t do much with California serpentine except admire it. For an example, see the ecstatic response of an out-of-state geologist to San Francisco’s Marshall Beach exposures.

Oakland building stones: Granite variations

29 August 2016


Oakland’s buildings embody history and geology in the different types of stone that compose their facades. So how about granite?

California began producing granite soon after statehood, in a stonecutting district near Sacramento where rail and barge transport was handy.

At the time Oakland’s third City Hall was being designed, around 1910, many large quarries in the Sierra were supplying the market, and the architects chose “Sierra White” stone from a quarry near Madera, probably the McGilvray Quarry. The same district still produces Sierra White granite for the great Coldspring empire.


This fine-grained granite is excellent for carving and for resisting the attacks of urban pollution. Its neutral color works well with the building’s superb ceramic tiles and marble. Many of San Francisco’s notable buildings (the St. Francis Hotel, Bank of California and Old Custom House among them) also use Sierra White.

Buildings of later vintage take advantage of stone from more distant sources. The Lake Merritt Tower building at 155 Grand Avenue, built in 1990, features a splendid granite with extremely coarse grains, not typical of California. The granite benches around the building use the same stone in a polished finish that displays it especially well.


The building itself employs the same granite with a flamed or thermal finish. It’s produced by running stone slabs through a set of gas-fired torches. The sudden thermal expansion shatters the minerals and, properly controlled, yields this rugged surface.


The Caltrans building next door, formally named the Nicholas C. Petris State Building and finished in 1992, is faced with a pink granite from Texas in both polished and sandblasted finishes. Here’s a closeup.


What are we looking at here? Time for the geology part. First of all, to stone dealers “granite” means only one thing — a coarse-grained rock (1) hard enough to take a good polish and (2) not marble, serpentine or quartzite — but that thing is a very broad one. Stonecutters came centuries before geologists, and what they say goes.

Geologists don’t call every granite building granite. “Black granite,” for instance, is gabbro. Scrupulous geologists would call all the stones in this post “granitoid,” meaning one of a broad set of coarse-grained rocks made of feldspar and quartz in various proportions. Real petrological granite has a narrower set of proportions. None of these stones has the 20 percent quartz that would qualify it as true granite. I know you’re disappointed. But the feldspar makes a great building stone.

In the picture above, quartz is the clear stuff that looks gray. Feldspar comes in two main types. The white grains are plagioclase feldspar, and the pink ones are alkali feldspar. (A pink color is unusual; it ranges from white to buff to red.) The black grains are typically hornblende, biotite (black mica) or both.

The gorgeous Texas Pink granite of the Lake Merritt Plaza complex, at 20th and Harrison streets, shows these minerals more vividly.


I do think this is Oakland’s most beautiful building stone. Texas Pink is a brand (not the kind you burn on steers), also from the Coldspring empire. It’s quarried from Granite Mountain, about an hour out of Austin and near the amazing dome of pink granite preserved in Enchanted Rock State Natural Area.

Texas Pink granite was also used, a bit more adventurously, in the AC Transit headquarters building at 1600 Franklin Street.


I don’t know in what year the building was constructed, but I have the impression that Oakland architects are finished with Texas Pink granite for the moment. Metal and glass is the default exterior of today’s large urban buildings. In their lavish lobbies and interiors, though, stone is still the right stuff.