Oakland Geology

_{The ruins of Morse & Heslop’s mill, Haywards, after the 1868 earthquake (Bancroft Library image)}

This week the media will mark San Francisco Earthquake Day, 18 April, as they always do but with an extra message for 2018 — this year will be the 150th anniversary of the original “Big One” in the Bay area, the Hayward earthquake of 21 October 1868. The U.S. Geological Survey and a host of partner agencies and organizations will roll out the next piece of a master plan that will guide the response to future large East Bay earthquake on our very own Hayward fault, usually called “a ticking seismic time bomb” by the intrepid researchers who get in front of cameras and audiences.

That first piece, Volume 1 of a planned series, is a scenario called HayWired: a description of a typical magnitude-7 earthquake, modeled after the 1868 quake, presented in as complete detail as we know how, with a special focus on its probable effects today in our highly electronic state. It’s online now at the USGS site.

I wrote about this project here last July, so you can read that post for more background. After that you may enjoy the USGS’s “geonarrative” about HayWired. It’s awesome, but only on a touchscreen device.

Today, though, I wanted to provide some details from the original quake. In 1868 a committee was convened to create a report on the event, but it never finished a report, so whatever work they did was lost. We only know as much as we do because after the San Francisco earthquake of 1906, the commission set up under UC Berkeley’s Andrew Lawson to investigate it decided to add a chapter on previous earthquakes. There were enough survivors of 1868 at the time to record quite a bit of detail. So here are some tidbits from the famous Lawson Report of 1908 about the Hayward quake of 1868.

The great shock happened about 7:50 a.m. on 21 October 1868, and ground ruptures were recorded, with 3 feet of offset in some places, from Mills College down to Warm Springs. North of San Leandro, though, “The county was then unsettled, and the information consisted of reports of cow-boys riding the range.” From Oakland we have these details:

• “A house near old Blair Park, in the present Piedmont district of Oakland, was badly damaged.”
• “Pans of milk and tubs of water emptied out almost in a moment, trees whipt about like straws; many houses twisted 5 or 6 inches out of square, particularly those on brick foundations.”
• “In Brooklyn, as in Oakland, many chimneys were broken off at the roofs.”
• “The bed of San Leandro Creek, which had been dry for several months, became filled with a stream of water 6 feet wide and a foot deep.”

At Haywards (the name of Hayward at the time) and neighboring towns, “nearly every house was thrown off its foundations.” Dozens of aftershocks were recorded in Haywards during the first 12 hours.

R.C. Vose of Roberts’ Landing wrote, “Our house broke in three pieces, each part falling outward. A boiler of hot water was on the stove, and with the first deafening jolt, the hot water came my way, giving me a bath I have never forgotten.”

In Fremont, Tyson’s Lagoon, the body of water next to the BART station, drained dry and remained dry for three years.

In San Jose, situated as it is in a large sedimentary basin, damage to brick buildings was universal.

12 aftershocks felt in San Francisco during the first day. Damage was most severe in the “made land” (artificial fill) in the former Yerba Buena Cove. Out at the Cliff House “the shock, however, did no damage, not even upsetting the glassware in the bar.” Ships at sea felt strong vibrations, like running aground or the anchor chains running out.

The earthquake was felt in Chico and many Sierra foothill towns, even in Carson, Nevada. Damaging shocks were reported throughout Sonoma County, as well as in Stockton and Sacramento.

All of this will happen again the next time a major quake strikes the Hayward fault. However, today there are hundreds of times as many people living in the affected areas. Back then, about 30 people died. Do the math and pay attention this week.

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.

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, in 2018.

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. (Update: Volume 2 has been released on schedule)

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.