Oakland City Hall: Stone and structure

24 November 2014

A few weeks ago I set foot inside our City Hall—for the first time, I’m embarrassed to say. I hope you will step inside before you’ve lived here 25 years, like me. I’ve always known we have a gorgeous building, and now I’m amazed. C’mon in.

cityhallcorner

First we’ll have a look at the structure’s famous seismic retrofit. See the light-colored strip at the foot of the walls? That’s a steel apron that covers an air gap all the way around the building. That gives the structure room to shimmy and sway on its fancy rubber feet during a severe earthquake. You can see it better by the side door, on 14th Street.

cityhall-skirt

Notice the bellows-style barrier on the building below the street level, filling that air gap.

When you go inside there’s a little exhibit space that has, among other interesting objects, this cutaway model of the base-isolation pads.

cityhall-pad

There are more than a hundred of these under the building, each one the size of a cafe table, made of thick rubber and lead plates. In the early 1990s, when City Hall was retrofitted, no one had ever used this technology at such a scale before. Since then many other precious historic buildings have used it. Hearst Mining Hall on the UC Berkeley campus is one.

OK, now comes the luscious stuff. The interior is beautiful in the way people favored a hundred years ago. Here’s the grand stairway leading from the front door up to the City Council chambers.

cityhall-balustrade450

Click the image for a large version. The balustrade is translucent marble on top, ceramic tiles on the sides. The stairs are marble. The ornamentation on the walls is plaster.

Here’s a skylight on the upper floor, edged in black marble.

cityhall-skylight

And this thing is a large lighting fixture that illuminates the rotunda. Click that photo for a large version. It was futuristic in 1914, and it’s still futuristic today.

cityhall-light450

There are other, smaller fixtures elsewhere on the ceiling that are worth searching for. The bronze ring suspended above the big ball depicts personifications of the planets—eight of them, from Mercury to Neptune, just like today.

Claremont chert, and other Oakland rocks, in Sunol

16 November 2014

The other day I took a field trip to see the construction site of the new dam for the Calaveras Reservoir. (The old dam is being replaced because it’s not strong enough to endure a big earthquake on the Calaveras fault, which runs essentially right through it.) It was a cool time, with fossils and big construction vehicles and engineers and grout. As the dam people were orienting us that morning, they passed around specimens of the major rock types in the area, and here was a fine chunk of chert from the Claremont Formation.

Claremont-in-Sunol

The stuff in our Oakland hills is white, because its carbon content was been leached out. This deep specimen retains the organic remains of ancient plankton that make the Claremont, like its larger sibling the Monterey Formation, source rocks for petroleum. (I showed you an exposure of similar stuff down at Alum Rock Park a while back.)

What the heck, I’m not planning to publish these anywhere else: here’s a cobble from a conglomerate down there that’s been stretched and fractured by activity on the Calaveras fault. It was exactly like the examples in our own Oakland Conglomerate.

calaverascobble

I think this one was from the Berryessa Formation (which is also found up at Alum Rock). Considering the looseness of the definitions of these formations, I feel safe in correlating them, although Crittenden defined the Berryessa as lying above the Oakland. Anyway, the phenomenon is the same.

One major feature of the construction project is an enormous cut made into the hill on the west side of the dam site. Basically, they discovered an active landslide there and decided to excavate the whole damn thing. We got to wander out along this exposure and hunt for fossils in the Temblor Formation, or at least rocks mapped as the Temblor.

calaverascut

There were a fair number of big ol’ scallop shells to be found, usually in pieces. Also some coaly bits of fossil wood. This is a rare exposure of an actual bedding plane, as marked by a pavement of scallop shells in what looks like their growth position.

calaveraspectens

We also learned a lot about the recent project that rebuilt part of the Hetch Hetchy Aqueduct that runs through here. Once the work was done, this tunnel-digging machine became surplus.

calaverasdigger

The guy asked us if we wanted to bid on it. I thought it had the makings of a good Burning Man stunt.

The Wild Oakland walk on the Hayward fault

9 November 2014

Saturday I led a walk for the members and friends of Wild Oakland to show off one of Oakland’s most striking places to encounter the Hayward fault. There was a nice turnout, about 60 people. I was glad to see so much interest. I hope that this post will enable those people, as well as all of you readers, to visit in person and learn more.

Here’s the route we took. It was just over 3 miles, although the altitude gain in the middle made some people bail out. Next time I’ll try to have alternative routes for their benefit.

WildOakwalkmap

The numbers refer to the stops during the walk. The asterisks refer to direct evidence of the fault’s activity, both on and off the day’s route.

Next is the same map with topography added. The thrust of the day’s exercise was to tour some distinctive features that the Hayward fault has left on the landscape.

WildOakwalkmapterrain

Stop 1, where we started, is where Arroyo Viejo does its abrupt 90-degree turn on its way from the hills to the bay. The right-lateral Hayward fault has dragged the Bay side of the landscape to the northwest, and the creek has had to bend in response.

WildOakwalk11-14-1

It’s a vivid example of how plate tectonics works in California, caught between the Pacific and North America plates. As the Pacific plate moves northwestward, pulled in that direction by subduction zones off Japan and Siberia and Alaska, it moves sideways—right-laterally—with respect to North America. That distorts the courses of streams that cross the boundary between the two plates. That plate boundary is a wide zone with three main sets of major faults running along it. The Hayward fault is in the middle set.

At Stop 2 I was able to point out a good example of creep offset, where the curbs on both sides of Encina Avenue have been cracked and shifted by creep (slow motion, less than 10 millimeters per year, without earthquakes) on the fault.

WildOakwalk11-14-2

Stop 3 gave us a decent elevated view of the fault zone from the Oakland Zoo grounds through that offset valley of Arroyo Viejo. (Here’s an earlier post showing the other direction.)

At Stop 4 I pointed out another probable example of creep offset, and everybody turned on cue to look at it.

WildOakwalk11-14-3

Stop 5 was at a highly disturbed bit of ground on Ney Avenue. The scarp crossing the road appears to be the head of a landslide right on the active trace of the fault.

WildOakwalk11-14-3a

Stop 6 was on a hilltop in the King Estates Open Space with a high view over the fault zone and the rest of the Bay area. The set of smooth-topped ridges extending into the valley of Arroyo Viejo have been cut off to form shoulders, and the dramatic shutter ridge on the right is the landform that has forced the stream to run sideways around it instead of straight to the Bay as it would prefer. (Here’s an earlier post about this same view.)

WildOakwalk11-14-4

I am quite taken with King Estates, and I believe it to be the largest piece left of the East Bay hills’ original landscape of grasslands. As the rains come this winter, I hope some Wild Oaklanders will poke around and examine it closely. For most or all of the people who came, it was their first visit.

click for 900-pixel version

Along the way is this nice little example of a landslide.

WildOakwalk11-14-5

The King Estates hills are mapped as alluvium of an earlier generation than the Pleistocene alluvium that makes up East Oakland’s low hills. I wonder two things about them. Are they a pressure ridge, pushed up by compression across the Hayward fault? (I noted that the fault’s motion is 90 percent strike-slip and 10 percent compression.) And what is to be learned from the blend of stones that practically forms a pavement on the hills?

WildOakwalk11-14-6

Stop 7 was a view into the watersheds of the three creeks above the fault: Rifle Range Branch, Country Club Branch, and Arroyo Viejo. And Stop 8 was in the valley of Country Club Branch, so close to its neighboring streams but so well separated from them by elevated divides. I blame the fault, which keeps jolting the countryside out of the equilibrium it seeks.

For dessert, I present a portion of Jim Lienkaemper’s 1992 map of the fault, which has annotations about the detailed evidence along it.

WildOakwalk11-14-features

The features marked G are geomorphic—things geologists notice in the landscape. Those marked C are hard evidence of creep—offset curbs (rc), sidewalks (rs) and fences (rf), and at Stop 2, echelon cracks (ec) across the road that have been erased by road repairs since 1991 when the map was compiled. You can download the whole map and consult the updated version from 2008 if you like.

Geological issues in the 2014 election

31 October 2014

Nobody asked for my guidance in this fall’s elections. That’s OK—this isn’t guidance, just a few observations from October.

The mayoral candidates in Oakland, almost unanimously, have ignored the two geological elephants in the room. First is the Hayward fault and its chronic threat to this wonderful city. Oakland is the upcoming victim, at some time unforeseen, of a magnitude-7 earthquake that will rip the ground all the way from beyond Sheffield Village to beyond the Claremont Resort. And ten times as many magnitude-6 events, the size of the 24 August Napa earthquake, will arise from the same stretch of the fault in the next century or so. Second is the rising sea level, which within our children’s lifespans will lap onto the waterfront and airport.

But those aren’t really election issues; they’re policy issues. We have staff making plans and pushing them forward an inch at a time, about as fast as the Hayward fault creeps. I’m sure that our next mayor, whoever it is, will support them fully. One of those plans is aimed at our large stock of vulnerable buildings—soft-story apartments. These multifamily dwellings, many of them fine old buildings, house some 20,000 people. In forecasts of the Big One, fully two-thirds of the Oakland residents made homeless will come from this class of structure. The city has mapped them, and when you contemplate the map maybe you’ll start thinking of them the way fire officials think of old-growth eucalyptus stands.

oaklandsoftstorymap

The Oakland Soft Story program has made good progress this year. Mayor Quan and Councilor Kalb got a task force together in April to get an ordinance ready for early 2015 that will concentrate on this low-hanging fruit of civic resilience, and I commend them both. (City Manager Henry Gardner published an excellent memo this month on the status of the program.) Dan Kalb isn’t up for re-election this year; Jean Quan is. Quan also is the only one of the mayoral candidates to mention earthquakes on their websites. She has a lot going for her, from my parochial viewpoint, like her support for the geology sign at Joaquin Miller Park. She took the time to show up at the Loma Prieta 25 policy conference on October 16, where she presented a spirited defense of the city’s earthquake preparedness efforts.

She gets it. I didn’t vote for her, though, because I think at least three other candidates will make better mayors. It’s OK if you disagree about that. But I trust that all of the likely winners will carry on correctly, with goading from Dan Kalb and skilled assistance from our Chief Resilience Officer, Victoria Salinas. Both of them get it, too.

That’s earthquake preparedness. Nobody’s talking about sea-level rise, but a lot of people are thinking about it, and I believe we’ll make the necessary adjustments in a timely way. It happens that the subject is on Salinas’s radar. If you never heard of her before, it’s because the Chief Resilience Officer is a grant-funded position that just started this year. I very much want her to succeed and be supported here after the grant runs out. Again, not an election issue.

On the state side of the election, I have less to say. The big water bond, Proposition 1, will direct some money at the Delta levees, which is an enormous area of vulnerability to earthquakes and sea-level rise. The more money the better, I say.

And in the Secretary of State election, I believe in Alex Padilla. He was off my radar until he sponsored the legislation for the statewide Earthquake Early Warning network last year. And last month at the Third International Earthquake Early Warning Conference, he showed up and seemed quite at home among the scientists and emergency-response people who care deeply about this technology. Turns out he’s a trained mechanical engineer, and as state senator for the district including Caltech, he regularly visited the school to keep up with the science there. It was by chance during one such visit that he got wind of the ShakeAlert early-warning system, and to his credit he took up the issue and carried it over the goal line. I believe that as Secretary of State, he would do the right things for the state’s voting technology. Actually I’m sure Pete Peterson would do a good job too, but I want to reward Padilla for good behavior even if he never deals with earthquake stuff again.

BTW check the Announcements/Q&A page about a walk I’ll be leading on November 8.

Penjing—in Oakland?

25 October 2014

Havenscourt Boulevard is a handsome street—wide, with a row of large palms up one side and offering nice views of the Seminary gap and the low and high hills. Then there are the homes, where I spotted this creative use of a roof drain.

penjing-havenscourt2

The water runs down a chute to a stilling basin, where it gently wells over the rim and waters the lawn. And the structure is outfitted with miniature buildings and picturesque rocks in a nice example of the Chinese art of penjing.

penjing-havenscourt

Penjing is related to the Japanese art of suiseki, but is not as abstract. Instead of suggesting ideal forms through the prism of naturally formed stones, penjing uses stones and models to depict landscapes, more or less fantastic, in miniature scale. It can range from kitschy to sublime. This example is what I would call homey, and very Oakland.

Loma Prieta plus 25

17 October 2014

Yesterday I attended the Loma Prieta 25 Symposium at the Kaiser Center. It was a quake geek’s Woodstock, where a motley host of experts got together to schmooze, celebrate 25 years of progress since the 1989 earthquake, and look ahead. At 10:16 a.m., along with 27 million other people around the world, we participated in the ShakeOut drill.

dropcoverhold

Since the Loma Prieta earthquake, Caltrans has finished reinforcing all of the state’s freeway overpasses, EBMUD and Hetch Hetchy have strengthened their principal water mains where they cross the Hayward fault, BART has strengthened its tracks and stations, and PG&E has made huge changes to make the power and gas system more robust. The airports and ports have been upgraded. The big bridges have been fixed or replaced (with only the Golden Gate Bridge upgrade to go).

The work done since Loma Prieta has also made governments work better. The mayor of Napa, Jill Techel, had high praise for the city, county and state emergency service agencies. She said PG&E did a wonderful job during the August earthquake. The federal agency FEMA was on top of things too. And the regional authority ABAG, the main sponsor of the symposium, was charged with energy and ideas to piggyback on the public awareness that followed the Napa quake.

Magnitude-6 events like the Napa earthquake will happen 10 times as often as the “big ones” we’re warned against. Even if the big ones will surely overwhelm some aspect of our preparations, the mitigation and preparedness in place can work wonders with the smaller events like the Napa quake.

The next steps that the experts laid out, the things they want done by Loma Prieta 50, involve increasing the Bay area’s resilience to disasters. Resilience means that people will not just avoid death and injury from a major earthquake, they’ll stay in their homes and return to their jobs quickly. The work of upgrading the infrastructure needs to move beyond the backbones to the limbs and arteries: neighborhood water and gas lines, smaller bridges, individual privately owned buildings. Oakland is ready to begin a program aimed at some 1800 soft-story residences in the city. The state’s earthquake insurance chief and the state senator heading the Insurance Committee were there to describe the advances they want to make in 2015. Progress works this way: inch by inch and year by year.

Emeryville

9 October 2014

The little town of Emeryville has almost no geology that passers-by would recognize. On the geologic map it’s displayed as largely artificial land and coastal alluvium.

emeryvillemap

The only people who see these things are builders and the geological professionals who advise them with their foundations.

The point was made from scratch—the original shore was a straight line pretty much where the railroad is now. Out at the end it’s been prettied up into Marina Park, a simulacrum of a wooded meadow. I like it there.

e-ville-point

A seawall, made of typical Franciscan riprap, protects it from the mild surf that manages to get here through the Golden Gate.

marinapark

The park-y part of Marina Park offers great views of Berkeley and points north. This is a good place to test your knowledge of the geography: Can you point out Strawberry Canyon, for instance. The highest point in this picture is Grizzly Peak.

e-ville-sculpture

We aren’t making any more artificial land in the Bay area, thank goodness. For a while there, people were planning to fill the whole Bay in. The nice thing about artificial land is that we can feel free to decorate it, whether formally as here or informally as at the Albany Bulb.


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