Archive for the ‘Oakland hazards’ Category

Soft-story buildings

8 June 2015

Let’s take a minute to think a bit about public policy. Think about when Oakland’s next major earthquake strikes. Remember, the Hayward fault is considered capable of causing an earthquake of magnitude 7.5 or even larger. According to a compelling memo by acting manager Henry Gardner issued last year on the 25th anniversary of the Loma Prieta earthquake, Oakland could expect tens of thousands of dwellings to be lost in such an event. An estimated two-thirds of the people left homeless will be those living in Oakland’s stock of about 1100 residential buildings built with soft first stories—with garages or retail shops on the ground floor—that are less sturdy against earthquake shaking.


I’m not saying that the particular buildings shown in this post are deficient—only a building inspector can determine that—they just caught my eye during a recent walk. Soft-story buildings that collapse will endanger more than just the people living in them. A large fraction of buildings that collapse will catch fire and threaten their neighbors. Each multi-resident building lost will displace many more people than a single-family residence will. And all of these buildings are owned by landlords. (See approximately 1400 of them in this preliminary app from Open Oakland.)


Steps that save these buildings from collapse will go a long way to reduce the misery after a big quake. With intact homes, people can stay where they are, sleep at night, resume their jobs as soon as possible, avoid becoming someone else’s problem and help get the city back on its feet.

The solution being slowly considered by city officials, last I heard, would loan landlords the money for specific quakeproofing projects, at nominal interest. The tenants would pay back all or most of the loan over a period of 20 years.

Let’s look at that. Let’s say a $10,000 project would strengthen a soft-story building by bolting it to a beefed-up foundation, bracing the walls with plywood and so on. It’s elementary stuff, but of course it requires permits and inspections and so on. Say the city makes it easy: interest-free money, rapid permitting/inspection, simple paperwork, protections for tenants against gouging and eviction.

Who benefits? Well we all do, from the state of California on down. The city ensures itself (and by “it” I mean “us”) of one more intact residential building after the Big One. The neighbors benefit even more, and of course the landlord does too. But the tenants get the greatest benefit. Tenants get to live in a building that won’t kill them or send them to the streets.

Divide the cost of that benefit into 240 payments—once a month for 20 years—and that $10k becomes $41.67. It’s not nothing, but the benefit is immediate, significant and permanent.


There is never any urgency felt about this kind of preparation. The ground is quiet and we have so many other problems. In the city manager’s memo, the city was making noise about putting a plan to the City Council early this year. Two weeks later, I wrote a long post on the subject for KQED Science.

And now it’s no longer early 2015, there’s nothing online, and all I’ve heard is a Twitter post a month ago or so quoting a staff recommendation that tenants pay 100 percent of the retrofit loans.

What do you hear? What do you think?

Trees and serpentine

29 March 2015

There’s a stretch of Castle Drive, up in the Piedmont Pines neighborhood, lined with huge trees. On the Walk Oakland map, it’s even labeled “Colonnade of Eucalyptus.”


These give me mixed feelings, as tree removal projects have aroused lately elsewhere in Oakland.

First, there’s the experience the trees provide. For one thing, you basically can’t walk here, so the colonnade is not a realistic attraction for walkers. Its main effect is a momentary diversion for drivers, who really don’t need one at this location.

Second, there’s the effect on the surroundings. As you climb up in this valley, the trees emerge as a very tall fence that blocks the view of the hills and the city and the bay.

Third, there’s the geologic setting. This part of the roadway runs along a very steep 40-degree slope through pure serpentinite, visible in the small landslide scar on the right side of the photo. Serpentine rock is poor footing for these massive trees. The trees may seem like they’re buttressing the roadway, but when they inevitably tip over in a storm or earthquake, they’ll uproot it instead, forcing the locals to drive up and down Ascot Drive for many months.

But how about that rock? Here’s a hunk of it that spilled across the road.


And here’s a hand specimen. I love this stone, but roadbuilders don’t.


It’s not my problem, since I don’t live there, but I think the best thing to do is to turn this colonnade into a line of ground-level stumps. The root systems would bolster the soil for another decade or so, giving the city time to plan and execute a properly engineered roadway. And bollards set in the stumps would preserve the trees’ most useful current function of keeping cars out of the canyon.

Trees are supposed to be wonderful stockpiles of carbon, sequestering it from the atmosphere. For me, that argument shouldn’t apply to individual trees or even individual groves of trees. What do we do, in the long run, with the carbon in trees—pile the trunks in pyramids? Carbon is best stored in the soil, where it provides excellent tilth and maintains a thriving ecosystem that resists fire and drought. It’s like circulating money in an economy: do you hoard it in vaults or spread it around among people ready to use it as a medium of exchange? Humans have spent thousands of years degrading the world’s soils, and I’d rather we begin to restore them.

The 2015 California Earthquake Forecast

11 March 2015

The U.S. Geological Survey issued a major update to its statewide earthquake forecast yesterday, the Third Uniform California Earthquake Rupture Forecast (UCERF3). No surprise, the news media boiled it down a little too far for my taste. For our side of the bay, there wasn’t a lot of change in my mind. Click the image below for a larger and wider image showing the whole Bay area. The whole report is online.


The Hayward fault is now officially considered to have a much higher risk of a very large, magnitude 7.5 or so, earthquake. (The figure in parentheses shows the percentage of the change in assigned risk.) This is because now we’ve added the possibility that not only the whole fault, but its neighboring faults (Rodgers Creek on the north and Calaveras on the south) could join it in an oversize rupture. Scientists (and I) have known about this change for a while because we follow the literature, but the new forecast is a formal admission.

The headlines and radio blurbs have been easy to misinterpret. The Tribune this morning was typical: “CALIFORNIA’S CHANCES OF ‘BIG ONE’ GROWING.” But look at it this way. The state of the Earth’s crust is hardly different from what it was seven years ago when the USGS issued its previous forecast. It’s we who have changed—our knowledge and models have progressed. We have a better idea of California’s chances of a “big one.”

The people who will study this in detail are doing things like setting earthquake insurance rates and designing large structures. For the rest of us, there is no change. We still live in earthquake country. We still need to work on our personal readiness. The largest events still will be rare. Better for Oaklanders to prepare for the smaller but still destructive magnitude-6 earthquakes, like the one in Napa last year. We will experience more than ten times as many of those, and they are worrisome enough.

What I like about the new forecast is that it isn’t really a forecast. The system has grown in sophistication and flexibility to the point that it’s really a modeler’s sandbox, a software environment that can handle surprises, new information and complexities better than ever. Talk to a seismologist and they’ll instantly agree that earthquakes pretty much always take us by surprise. The giant Tohoku earthquake, which happened four years ago today, took seismologists by surprise. You name it, the quake was a surprise. It will be many decades, maybe centuries, before this state of affairs ends.

We can’t deal with the situation using simple, linear computer models based on one idea of Earth’s behavior. The third UCERF is a supple, fine-grained instrument that takes advantage of many significant advances during the last decade. When I told a USGS quake guy yesterday how much I admired the new model, his eyes twinkled. They’re proud of this.