Archive for the ‘Oakland hazards’ Category

The McKillop landslide: Ten years after

17 July 2017

In December 2006, I read a series of news stories about a landslide in Fruitvale, on McKillop Road, that took out a house and threatened two more, so I checked it out and was so impressed I wrote it up for About.com. This house was the victim.

And this was its front yard. When I revisited, last week, the three concrete steps were still there and the little pine tree next to them was over 20 feet tall.

This slump was the extension of an adjoining land failure earlier that year. In 2006 I was able to make my way across the top of that older slump and take this shot from the other side.

Nowadays the scene is well secured and overgrown with brush, but nevertheless the land is basically ruined. The city is storing some stuff there, and there are some beehives.

You can’t really fix landslide scars. On the human scale, they’re permanent. And landslides tend to feed on each other — when a portion of a slope fails, the adjoining slopes often follow. That’s the case on McKillop Road. William D. Wood Park is actually the scar of much larger landslides that have occurred, according to one report, since 1909.

The Oakland Tribune reported in 1936 after one such slide, “The property upon which the houses were built was originally filled-in ground from excavations made at the [Central Reservoir] site 15 years ago, neighbors said.” Throughout the 1940s and into the 1950s, it was routinely called the city’s worst landslide. Studies were made along with attempts to stabilize the slope, to little avail. Homeowners were putting their houses on jacks.

Everyone gave up fighting nature in the 1970s, and they made the land a park. And so far so good — here it was in 2006:

And how it looks today.

Nature may not have given up fighting us, though.

HayWired, an imaginary earthquake coming in 2018

3 July 2017

Earthquakes are always a surprise, but we can be ready for them. Or, more ready. We can practice on a household basis, whether it’s a simple “Drop, Cover, Hold On” drill or a series of family meetings to go over scenarios — what if Mom’s stuck at work? What if we’re all out of town? What if we’re separated? What if our home is red-tagged?

It can be complicated. And think of how a whole city or region might practice for a major earthquake. The first requirement is a realistic picture of what would happen — a detailed, scientifically based earthquake scenario. When geologist Dale Cox first started talking to disaster responders about earthquakes, what they wanted to know most was “What exactly will the Big One be like?” He realized that his colleagues at the U.S. Geological Survey could supply realistic answers based on their research and “get the science used.”

Last week Cox told an audience at SPUR about a new scenario in the works for the Hayward fault, named HayWired. We’ll hear a lot about it on the Bay area’s unofficial Earthquake Day, April 18th, next year.

For scenario work, every region needs its own custom earthquake. Ten years ago, the first ShakeOut exercise in Southern California used a scenario quake measuring magnitude 7.8 that ruptured the San Andreas fault from the Salton Sea all the way to Lancaster.

For the Hayward fault — what Cox called “the most urbanized fault in the United States” — planners of the Hayward Fault Initiative have used a repeat of the magnitude 6.8 earthquake in 1868. They’ve also used a 7.0 quake that, unlike the 1868 event, would rupture the fault’s entire length. The new-and-improved HayWired scenario takes everything to a new level of detail and engagement.

Alameda County Courthouse before and after the 1868 Hayward fault earthquake. San Leandro Public Library (before) and Bancroft Library (after).

The HayWired scenario starts with a scientific description of the hazards connected to a hypothetical magnitude 7.05 earthquake that occurs on Wednesday, April 18, 2018 at 4:18 in the afternoon. It goes into far more detail than previous efforts, covering ground motions, landslides, liquefaction, fires, disruptions to communications and the digital economy (hence the “Wired” part of the name), and aftershocks and afterslip.

Aftershocks in the first two years after the HayWired earthquake. The largest aftershock, of magnitude 6.2, is a pretty major quake in itself. USGS image.

That description has been published as the first of three volumes. Other specialists are preparing two more volumes based on it, one on environmental and engineering impacts and the other on social and economic impacts. Those will come out in the next few months.

The HayWired earthquake originates in Oakland, 8 kilometers beneath the intersection of Skyline Boulevard and Joaquin Miller Road. For that and many other reasons, I’ll be following this project closely for you.

Oakland builders, what are you thinking?

12 June 2017

Californians have always known we’re prone to earthquakes. The first Californians didn’t have our worries about it, though, because their structures were small and limber, no larger than a temescal sweathouse. Things changed when the missionaries of New Spain came into the country starting in the late 1700s. When the earthquake of 8 December 1812 took down the six-year-old stone church at San Juan Capistrano during the day’s first service, the forty natives who died were probably the first Californians ever, in thousands of years, to be killed by a structural collapse from an earthquake.

To the Americans who succeeded the Spanish and Mexicans in the Bay area, earthquakes were well known. By my count, after Oakland incorporated in 1852 its inhabitants experienced thirteen notable earthquakes in the 54 years before 1906. As the American cities grew up around the Bay, builders sought to guard against quakes with thick walls of ever-stronger materials, culminating in concrete and steel. In the century since the 1906 San Francisco quake, engineers and architects have repeatedly improved the building codes.

Today, buildings of almost any shape and size can be designed to withstand the largest earthquakes. That doesn’t mean we’ll trust them. Just as some of us get vertigo looking at photos of confident rock climbers, appearances can outweigh reason.

In recent months, two large buildings have been proposed in downtown Oakland that actually included overhangs. The one originally submitted for 325 22nd Street, facing the Ordway Building, looked like this, with a cantilevered soffit (as seen on SocketSite).

The Planning Department didn’t like its bulkiness and awkward fit with its neighboring buildings, so that design was replaced with a more traditional set of boxes.

The other building site is at 1100 Broadway, the lot next to the old Key System Building, both of which have been vacant since the 1989 earthquake. The latest project, from new owners Ellis Partners, is supposed to renovate and integrate with the Key Building, and this overbearing design is what they came up with last month.

After getting feedback from planners and the Oakland Heritage Alliance, they submitted a revised design last week. They just love that looming cantilever — in fact they added more on other sides.

Builders and planners are pros, so the overhangs are designed to hold. I understand that very well in my head. But how many of us will feel secure beneath — or inside — a cantilevered structure?

The National Earthquake Hazard Reduction Program (NEHRP) has funded and published research into building standards since the 1970s. Its publication Earthquake-Resistant Design Concepts spells out seven characteristics that are necessary for buildings in areas prone to large earthquakes. Two of those are especially pertinent for cantilevered designs: continuous load paths and regularity. The first means that the forces a quake imposes on a structure need to be guided down to the ground. The second means that irregular buildings must be extra strong, as “the damage can be concentrated in one or a few locations, resulting in extreme local damage and a loss of the structure’s ability to survive the shaking.”

I think these are obvious to most people, and that’s why, say, the new Kaiser hospital is reassuring in its continuity and regularity. The Transamerica Pyramid, even the new Salesforce Tower — reassuring.

The design for 1100 Broadway is a textbook example of discontinuous and irregular, especially in its integration with the hundred-year-old, damaged Key System Building. The NEHRP Concepts classify downtown Oakland office buildings in Seismic Design Category E, just short of the most stringent category used for hospitals, police and fire stations and other critical structures.

After the East Bay’s next big earthquake, our perceptions will change. It’s important to think about that. Old-timers who were here for the Loma Prieta quake in 1989 can tell you. For years afterward, this fine old town will feel like Doctor Caligari’s city, angular and foreboding.

When large quakes strike, buildings can sustain damage in an earthquake and then collapse in aftershocks, of which we will have plenty after a magnitude 6.7 event. I use that magnitude because the official odds are based on it, and they give the Hayward fault a one-in-three chance of producing one before the year 2043, within the useful life of these proposed buildings.

No one alive has experienced such a quake in Oakland. Once we do, buildings with overhangs, even if they perform superbly, will no longer look vibrant or stylish — they’ll look deadly to our newly cautious eyes. And with that they’ll be effectively worthless, except maybe for low-income housing (which would be a good thing). And the city that thought such a building was a cool statement will be judged for that statement.

I submit that builders and the city should be very conservative in not just their designs, but the appearance of their designs.