Archive for the ‘Earthquakes’ Category

Earthquake apps and post-quake observations

16 October 2017

Seems like disaster is in the air every October. This year the catastrophe is wildfire in the North Bay, bringing up memories of our own turn in the line of fire this very week in 1991.

Yesterday the local paper published an article by Seung Lee that explicitly linked the October fires of 2017 to the Oakland Earthquake of 20XX, not here yet but sure to come.

Lee pointed to some promising smartphone apps that could save us lots of anguish and maybe even lives. Of course, MyShake came first. It’s an Android app (IOS version pending) that turns your phone into a crude but effective, networked seismograph-plus-earthquake-alarm. I’m watching MyShake closely and will let you know when iPhones can participate.

Lee mentioned several apps to help with communications, offering flexibility in the face of degraded cell service and bringing more superpowers to your smartphone. They include Zello, which turns phones into crude but effective walkie-talkies; FireChat, which enables phones to network without internet or cell service by using peer-to-peer technology; and NextRadio, which turns last-generation phones into FM radios. Needless to say, a portable charger belongs in your purse and go-bag — fully charged.

But I’m also writing to point out some possibilities for us to help science after a large East Bay earthquake, once you’ve taken care of yourself and those nearby. Lots of geologists will show up, doing different things. Some will be inspecting damage as consultants. Some will be there doing science on behalf of state and federal agencies. Professors will come with their students, teaching them real-life lessons in disaster response and collaboration with other scientists. You can give them a hand during the aftermath. And some more things you can do of your own initiative.

If you see ruptures in the ground, collect some data. Measure their offsets, photograph them with date and time stamps, and insert objects for scale like a coin or lens cover or your own hand. Do these things quickly before city crews come in to fix the damage. Document offsets in buildings, too. Repeat these observations as the days go on, because afterslip — continuing fault motion once the shaking is over — is a new and lively topic among earthquake scientists.

Ambitious amateurs can practice the structure-from-motion (SfM) technique, by which a series of photos taken from all sides can be turned into accurate three-dimensional models. This yielded dramatically good images after the 2014 Napa earthquake. If I were a maker type, I’d do this. Any practitioners out there?

Monitor your local streams. As earthquakes rattle the ground, they shake down the material of the hills as surely as you’d shake down a jar of coffee beans. When this happens, groundwater gets pushed aside, and a sudden rush of water fills the streams for a while. The Napa earthquake of 24 August 2014 did this all over the North Bay, which I posted about at the time, and Oakland was affected, too. An Eastmont Hills homeowner whose property has a tiny backyard stream valley, dry most of the year, told me that he saw water rise in it within hours of the Napa quake, and the stream ran high for about two weeks.

The Oakland Earthquake of 20XX will be a Katrina-sized event, much worse than the Loma Prieta quake (another October surprise that happened 28 years ago tomorrow). The more we’re aware, the more we prepare, the less likely that our local Katrina will be our Katrina catastrophe. And let’s hope it picks a different month to strike.

In housekeeping news, I’ve pulled earthquake-related posts into their own category, mostly separate from posts about the Hayward fault.

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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.

Old fill and made land

6 March 2017

Between the 1840s and roughly 1960, the Bay area made colossal amounts of dry land through “reclamation,” a euphemism for filling in marshland with whatever was handy. Oakland was no exception. Here’s a portion of the geologic map centered on Jack London Square, Oakland’s original harbor. Reclaimed land, or artificial fill, is shown in pink.

jlsgeomap

We were lucky in Oakland that the waterfront was largely developed by the railroads. They had the money and foresight to do the job right, by mid-1800s standards, and the fill is pretty good. An exception is the building that houses Heinold’s First and Last Chance Saloon.

heinolds

The structure was built in 1880 of ship’s timbers, and in accordance with good practice it was placed on piles, driven into the fill and the mud beneath. But it has settled, especially after the 1906 earthquake, and the land has been built up around it. You won’t notice from the outside until you approach the door, which sits below the surrounding ground.

heinoldsdoor

Go inside (as every Oaklander should at least once), and you’re in a funhouse of ancient furniture and creaky walls covered with old papers, all set off by a crazily tilted floor. Fortunately it’s merely a bar and not some place people have to live in.

For real landfill folly, you’ll want to visit San Francisco. The land south of Market Street was originally a mixed bag — the bedrock of Rincon Hill and a ridge of sand dunes to its west offered firm ground, and Sullivan Marsh to their south surrounded Mission Bay with poor ground. On the geologic map, the old marsh is mapped as “Qaf,” or artificial fill. It extends to the Civic Center.

sfmarshgeomap

The area south of Market began to be developed around 1870, and the marsh was filled rapidly and willy-nilly. Within a few decades the good ground was occupied by grand hotels, office buildings and luxury residences while the bad ground — the made land — was full of working-class boarding houses, small shops and warehouses.

The marsh contained several meters of peat on the surface and saturated sand and mud beneath. Loading this land with landfill rubbish, then placing buildings on it, left it highly vulnerable to settling and, during earthquakes, liquefaction — complete loss of strength.

When the 1906 quake struck, the buildings on firm ground did well while the former marsh area was largely ruined. But everything south of Market, rich and poor, burned down within a day. All of it was rebuilt, just like before, as rapidly as possible. And for the next century, the made land has kept on subsiding.

Main streets, like 7th Street, were regularly built up to maintain their grade. Side streets like Natoma were not.

sfslump-4

Many homes sank at the same time the street were built up. This one is typical.

sfslump-3

At the same time, many buildings suffered differential or uneven settling, like Heinold’s did. Residents, then and now, just put up with it.

sfslump-2

Today redevelopment is replacing these tired survivers. The new blocks have a hip and trendy look now, if you don’t happen to notice the occasional straggler.

sfslump-1

Soon enough, the past will vanish from the South of Market. But just wait another century, or less if they have a major quake before then, and some of these new buildings will slowly turn into antique funhouses like Heinold’s.

Oakland has been pretty good about avoiding our own versions of Sullivan Marsh, but we do have strips of fill to watch out for.