Oakland Geology

^{Soft-story damage in San Francisco’s Marina district, 1989. Retrofit programs in Oakland aim at preventing this kind of destruction.}

As you all know, the Hayward fault runs through the middle of Oakland and the whole East Bay, and as you all know it will rupture some day in a large, destructive earthquake — a catastrophe on the scale of the 1906 San Francisco quake and fire, or Hurricane Katrina in New Orleans in 2005.

A large group of researchers led by the U.S. Geological Survey has been working with governments, insurers and others on ways to foresee what the earthquake will do, in hopes we can counteract the worst of it beforehand and cope better with it afterward. Their product is a detailed earthquake scenario, called HayWired, that enables planners of all kinds to work together in a coordinated way and come up with meaningful, actionable recommendations. I’ve been following the effort, and reporting on it here, for four years now.

Last week I checked in on the state of the effort in an online seminar by SPUR, the regional planning nonprofit, titled “Where Is Home after a Large Earthquake in the Bay Area?” (This and previous seminars can be found here.) Prompted by the release of new chapters in volume 3 of the HayWired report, it focused on rebuilding housing after the HayWired quake in the communities most at risk. Forgive the metaphor, but we have to light a fire under all levels of government and keep blowing on it.

The HayWired scenario earthquake is a magnitude-7 event that occurs on an April morning, rupturing the whole northern half of the fault from an initiation point under the Crestmont neighborhood. As the shaking ends, landslides grind their way down hundreds of hillsides, bayside ground turns to soup and almost 500 large fires are triggered. Some 800 people are dead, not counting deaths related to the fires. In the nine-county Bay area, a million buildings are damaged or destroyed. Property losses amount to $40 billion in Alameda County alone. These are the best estimates we know how to make.

That’s all before we get to the local impacts. A belt of badly damaged neighborhoods extends along the fault from Pinole to Fremont plus outliers in Novato, Pleasanton and Vallejo, but the community most at risk is all of East Oakland.

Even when the houses survive, neighborhoods don’t just heal. People will keep leaving heavily damaged areas, in “voluntary displacement,” for three understandable reasons:

1. They can’t afford to stay — their jobs fail, their money runs out, rents rise too high.

2. They can’t stand to stay — roads and transit and water are down for months and perhaps longer; schools and shelters shut down; aftershocks drive them nuts.

3. They don’t have to stay — they’re young, they’re mobile, they’re ready to go somewhere better.

Voluntary displacement was a notable factor after the 1994 Northridge earthquake, when neighborhoods turned into “ghost towns” as people kept moving out, especially where multifamily residences were common. In New Orleans it was even worse. And it will be a big consideration in East Oakland, where so many residents already have “vulnerability factors” like low income, language problems, youth and old age, and lack of education.

I’m almost done with the bad news. Government money will be slow in coming and far short of the need. Earthquake insurance will help individuals who can afford it, but no one will be made whole. And some areas will require a complete makeover, which will take years of planning and be politically fraught.

What can be done to help in advance? We have shoestrings of help like the state government’s earthquake insurance fund. We have the state’s Earthquake Brace + Bolt program that helped pay to strengthen 15,000 dwellings. (Until they announce more funding for 2021 especially for underserved neighborhoods, you can find qualified contractors on their website.) Oakland has a slow-moving mandatory retrofit project aimed at saving our existing housing stock from collapse. Those small-scale programs are laudable, but they won’t cut it.

Speakers at the seminar pointed to larger efforts. On the biggest scale, SPUR issued a report this year on fixing the Bay area’s massive housing problem over the next 50 years. Every new house or apartment is more earthquake-resistant than anything older, which is why I strongly favor housing construction at all scales. I learned the most from Maziar Movassaghi of the state Department of Housing and Community Development, who had hard-won advice from the 2018 Camp Fire disaster. Recovery has taken years because people couldn’t build new multifamily housing until the roads and infrastructure were ready, and then the financing took even longer. The bureaucracy is complicated, the money is tight and it all takes too long for people to endure. And all the while the pressure is to do the easiest thing — build back what used to be there — rather than the resilient thing — build something better.

What Movassaghi recommended was to have plans in place for housing recovery after disasters, the lack of which was a big obstacle after the fires. (He noted a good example from San Jose.) Funding agencies won’t just write a big check — a multiyear community development block grant — if your city can’t show them it knows what it’s doing. Such plans, he said, should be made jointly by community-development folks and emergency-management folks, to make sure the new neighborhood will come through the next disaster better than it did this one. Having good plans in place can save your city years of misery.

For most of us this kind of work is above our pay grade, but it’s within our horizon of concern. We can do what citizens do: listen, learn and lobby our public servants.

Previous posts:

HayWired, an imaginary earthquake coming in 2018

News from the HayWired fault

Earthquake advice for Oaklanders 4: What to do

The pandemic has eased enough that Mountain View Cemetery, the Bay area’s finest landscape, has opened its gates again to the public, though only on Wednesdays and Saturdays for the moment and with an earnest plea for your good behavior. Thus on Wednesday I was finally able to visit Plot 1, where the first earthquake victim in the East Bay’s history is buried: Joseph W. Josselyn. It turns out his monument isn’t the only one there with an earthquake connection.

William Halley’s 1876 Centennial Year Book of Alameda County reproduces the account of the great earthquake of 21 October 1868 from the next day’s Oakland News, giving us the picture of Josselyn’s worst day: “At San Leandro the earthquake was much more severe than in Oakland or Alameda, and not a building escaped damage. The saddest calamity was the death of Mr. J. W. Josselyn, Deputy Clerk, a young man of much promise and ability, who has for a few years past been in the office of the County Treasurer. He was crushed in the ruins of the County Court House. . . . There were in the Clerk’s office four persons besides Mr. Josselyn. Mr. Josselyn endeavored to escape by the front entrance to the building, and when passing the threshold the falling walls buried him in its fragments. The other persons, seeing the front give way, escaped through one of the windows.”

The courthouse (San Leandro being the short-lived county seat at the time) was newly built, and the shaking was said to have revealed its shoddy construction. On the other hand, the earthquake broke every chimney in San Leandro that foggy morning, so maybe the fault lay not in the building, but in the Hayward fault. The lesson learned after every major quake is always the same: don’t try to run outside while the ground is shaking. The way we state that lesson today is: Drop, Cover, Hold On.

Halley reported, “The lamented Josselyn’s funeral took place at 11 o’clock on the morning of the 23d of October, from the Presbyterian Church, and under the auspices of the Masonic fraternity. His remains were interred in Mountain View Cemetery, near Oakland, and over eighty carriages formed the funeral procession.” His fellow Masons did well by Josselyn, furnishing his grave with a fine sandstone stele with the Masonic square-and-compass emblem and some skilled carving.

I perceive a message in the emphasis the carver gave the date of Josselyn’s fate. This date was carved into local memory as surely as 17 October 1989 is in our own (in mine, anyway).

Michael Colbruno’s “Mountain View People” blog has a photo of Josselyn that gives a hint of his energy and popularity.

Behind Josselyn’s monument is the white marble stele of the Pardee family plot, one of the handsomest bits of Plot 1 with its upgraded frame of ornamental gravel.

Enoch Pardee, the patriarch, builder of the Pardee mansion, was a major Oakland figure in his time, but his son George, a figure of even greater renown, is the earthquake connection.

George Pardee was born in the earthquake year of 1857 and experienced the 1868 quake as a youth, but it was the 1906 San Francisco earthquake that marked his life the most. He was governor of California at the time, and he immediately took the train to Oakland to oversee the state’s response from his family home. There he welcomed refugees from across the Bay, many of whom stayed in Oakland in a great pulse of population and development.

The 1906 earthquake did much damage in Oakland, by the way, but here in the cemetery, according to Andrew Lawson in the 1908 Report of the State Earthquake Investigation Commission, “the chief damage done was the cracking of the receiving vault, and that was not injured very much. In St. Mary’s Cemetery, on the small ridge to the west, however, many monuments were moved or twisted and several were overthrown.” An observer counted about a dozen monuments disturbed here, mostly by twisting. (Lawson himself was buried at Mountain View in 1952, one of Mountain View’s contingent of noted geologists.)

The first thing to do about earthquakes in Oakland is PREPARE! Well OK, but prepare for what?

To get our attention, a team of federal and state geologists got together a few years ago and prepared an elaborate forecast of a seriously large earthquake on the Hayward fault, a magnitude 7 rupture from Point Pinole down to Hayward, and the whole process of coping with and recovering from it. They called it the HayWired Earthquake Scenario to emphasize the 21st-century vulnerabilities of the wired East Bay, where everything depends on electricity and the internet. The scenario was made to be studied closely by people of all kinds whose business is planning ahead. It will do for my purposes.

The HayWired earthquake starts with a rupture on the fault right underneath the Crestmont neighborhood in Oakland, and the rupture proceeds in both directions from there. Strong shaking lasts for a good thirty seconds.

Look around where you’re sitting and picture it. You feel as if two big strong people are shoving you back and forth between them. Impossible to stay standing. More big strong people are going nuts around you: knocking over your bookshelves and dressers, pulling everything out of your cabinets, smashing your aquarium and your floor lamps. Trees outside are snapping off limbs, vehicles on the road losing control. The lights go out. Your laptop flips to the floor, suddenly on battery power. The quake itself roars like a locomotive, and the buildings around you snap, crackle and pop. You hear screaming and car alarms and shattering glass. It goes on and on.

That thirty-second period is what “Drop, Cover, Hold On” is about. If you have the presence of mind to do anything at all, that’s all you should do. Drop to the floor. Take cover underneath something. Hold on to it. Forget about standing in doorways, forget about running somewhere, try not to shout useless things. This is why we have earthquake drills, to make this behavior a life-saving reflex.

The hard shaking will stop after that endless thirty seconds, succeeded by a lot of reverberations and aftershocks. As soon as you can, get up and deliberately make ready to leave, even if everything seems okay for the moment. This is the stage I’m talking about when I say PREPARE. For details, start with Ready.gov or your own favorite preparedness site.

A couple other things. Stay nearby; don’t try to skip town in your car. Don’t tie up the phone system; text one out-of-town contact and save your phone battery. And be prepared to wait; everything will take time. I made these points in more detail in another post.

We have a hard time facing the threat of large earthquakes. The prospect rouses fear, and too much fear is paralyzing. I suggest thinking in terms of three categories, a set of three mental lists, labeled “Face it,” “Calm down” and “Perk up.”

Face it

I can guarantee you that the Big One will be worse than you imagine. Face it. Bad as it will be, though, that part will pass in less than a minute. The aftershocks, in their own way, will be just as bad, and they’ll go on for months. Maybe this is more of a “thinking about it won’t help” list. Move on to the second list.

Calm down

The Big One will kill hundreds of people, but I can also almost — almost — guarantee that you won’t be one of them. Calm down. If even 1000 people are killed in the East Bay’s population of 2.5 million, the odds against you are so small you can ignore them. Pay attention to the more realistic threats that will hinder your life, not kill you. That leads to the third list.

Perk up

Think about the different spaces in your life — where you sleep, where you work, where your most important stuff is — and come up with tangible ways you can prepare. Perk up. For instance, there are apps, there are ways you can look forward to helping science. Other things that perk me up may appeal only to other geo-geeks, but they include visiting the fault while it’s still sleeping, and the occasional game of quakespotting.

Back in my first post of this series, I said I was thinking about earthquakes because we’re in a year of disasters, and the kind of disaster I know the most about is earthquakes. The reason this really matters to me right now is that while every disaster changes us, every disaster ends. In effect, the aftermath is a new age.

Oakland’s last earthquake, in 1989, changed everyone who went through it — it imposed a certain solidarity upon us. And almost all of the wounds the quake gave us have healed stronger. Damaged buildings have been replaced or renovated.

Freeways and water mains and power lines have been strengthened. Households are better prepared and rehearsed. The city is requiring residences to have their dangerous soft stories fixed.

The disasters of 2020 have affected areas larger than Oakland or even the Bay area. Wildfires have struck huge regions, the unemployment crisis has hit the whole state, and the pandemic is a national tragedy. But they’ll all end. The Trump administration will end. And the next big earthquake, in all its instant and drawn-out consequences, will end. A time will come when we can make some long-awaited changes and build back wiser and better.

This set of posts addresses Oakland’s seismic situation, but that’s only one of the natural hazards we’re prone to. There’s also the complication of living not just with earthquakes, but with everything else about California, like our droughts and floods, our heat waves and landslides, our wildfires and our economy. Earthquakes have intersectionality with all of these other risks — what we do about those risks affects how we act with respect to earthquakes, and vice versa.

For example, landslides can be triggered by winter rains or earthquakes, so consider a big earthquake in winter. As I wrote here for the 150th anniversary of the last big East Bay earthquake, “If we’re lucky during the next big quake, as we were in 1868, the ground will be dry. If we aren’t, and the ground is waterlogged, well, heaven help us because we’ll get both kinds of landslide at once.”

In that perspective, the growing gorilla in the room (to mangle a metaphor), the one that makes all the others worse, is climate change. I thought that Benjamin Hatchett of the Desert Research Institute, in Reno, summarized the situation well in a recent paper about atmospheric rivers: “California’s complex terrain, biogeographical diversity, proximity to the data‐sparse North Pacific Ocean, and large population and economy provide an environment both dependent upon and highly susceptible to weather and climate extremes. These include extreme precipitation events, flooding, land‐surface mass wasting, multiyear droughts and pluvials, heat waves, and wildfires. Many of these extremes are projected to worsen or become more impactful in a warming climate.”

Climate change will force all of us in this civilization, leaders and neighbors alike, to up our game.

The first two posts in this series were about the Hayward fault itself in Oakland and about the different types of ground in Oakland that earthquakes on the fault will affect. This post goes into some details about the kinds of earthquakes we can expect in Oakland. I’m going to try and ignore all the interesting complexities — the subject is full of rabbit holes to go down — and keep things really simple.

Earthquakes are a release of energy that is stored in the rocks along and near the fault surface. The energy comes from the movements of the great plates of rigid rock that form the outermost skin of the Earth. Oakland sits in the middle of a wide boundary between the Pacific plate on the west and the North America plate on the east. In the grossest terms, the Pacific plate is sliding quickly northwest and the North America plate is moving slowly west, pushing against it like a semi merging onto a busy freeway.

The input of energy into the fault from plate tectonics is extremely steady, while the output of energy from the fault — in earthquakes — is pretty much random. That’s the essential mystery at the heart of earthquake science.

At our latitude, that wide boundary between the Pacific and North America plates extends from the San Andreas fault, across the Bay, to the Concord and/or Calaveras faults over the hills. Each of those faults takes up part of the overall motion between the plates. They’re basically long, vertical cracks that extend downward about 13 kilometers — below that depth (8 miles), the rocks are too hot and soft to crack and instead they just deform like modeling clay.

^{From the USGS Earthquakes Map}

The energy that earthquakes release builds up steadily in the Earth’s crust along the two sides of the fault. Friction keeps the two sides from sliding past each other. We say that the fault is locked. Instead, the rocks slowly warp, exactly as if they were great blocks of rubber. And at some point the friction is overcome, the fault ruptures, the rocks spring back into shape, and that elastic energy is released as an earthquake.

(This is where the math kicks in! Various well-known laws of physics allow us to turn my word descriptions into actual equations, and science can exert its superpowers. Careful measurements and creative mathematics give us ever-better answers to ever-deeper questions, and seismology, the study of earthquakes, has progressed into a vibrant field of science with important problems to explore. This paper by Rundle and Donnellan on earthquake clusters is a fresh example of research on the leading edge.)

An earthquake’s magnitude is based on how much the ground moves back and forth (or up and down), as measured by seismographs. Each unit of magnitude represents a factor of ten: if a magnitude-4 shaker moves the ground by a millimeter — not much but definitely perceivable — a size-5 event would move it a centimeter. The same unit of magnitude represents a 32-fold difference in the total amount of energy released, because the geometry is different. (The U.S. Geological Survey has a page with more detail about magnitudes.)

The amount of energy in an earthquake depends on how big a patch of the fault gives way. The largest possible earthquake, then, would happen if the whole thing rips. And how big is the whole thing? We used to measure the Hayward fault as 120 kilometers long, from Point Pinole to the hills east of San Jose, enough to generate a magnitude 7.0 quake. In 2016 we learned that the fault is directly connected to the Rodgers Creek fault in the North Bay, which extends up to Santa Rosa. The combined fault is roughly twice the length of the Hayward fault alone, and it could produce a magnitude 7.4 quake. That’s getting close to the size of the 1906 San Francisco earthquake (about 7.7), and it would tear right through Oakland.

That’s the largest possible earthquake — and also the least likely. There’s a strong element of chance in the way that ruptures grow. A rupture starting out does not “know” how big it will become. The growth of a rupture is more like a run of luck at a casino. Our earthquakes generally don’t rupture the ground surface unless they’re larger than magnitude 6 or so. Those, we have a hope of detecting in the ancient sediments along the fault.

Studies made by digging trenches across the Hayward fault have given us a fair idea of its history of large earthquakes. There seem to have been six in the last 900 years and a dozen in the last 2000 years. Age estimates are fuzzy, but these events aren’t very rhythmic. Their average rate is one every 160 years, but the time between these major ground-breaking earthquakes has ranged from 95 to 225 years.

It’s been 152 years since the last one on 21 October 1868, which had a magnitude estimated at around 6.8. While that matches the average rate, these things aren’t like clockwork. Earthquakes aren’t scheduled. Therefore the next Big One is not “overdue.” Nevertheless, it appears that enough stress has accumulated on the fault since 1868 to power another event of about the same size. The scientific authorities say that a large earthquake (magnitude 6.7 is the size they picked) has a two-in-three chance of happening by 2043 somewhere in the Bay area. Half of that probability comes from the Hayward-Rodgers Creek fault.

What about smaller quakes, like magnitude 5 or greater? These would be strong enough to knock down things like chimneys and crack walls and windows. The area around the Hayward fault has had maybe 20 since 1850, as shown in the map below.

^{Magnitude 5 earthquakes since 1850 within the box including the Hayward fault, from the USGS catalog search}

But since 1889, only three were actually on the Hayward fault (5 September 1955, 13 June 1988 and Halloween 2007). Historically (aside from 1868), Oakland has suffered more from large earthquakes elsewhere in the Bay area than from homegrown ones. The most recent of those were in October 1989 (Loma Prieta, magnitude 6.9) and August 2014 (Napa, magnitude 6.0).

We’ve been lucky. But luck is a human concept, not a geological fact. There is a hint in the Bay area historical record (documented in this 2002 paper and elsewhere) that big quakes have been preceded by clusters of middle-sized ones. Or rather, big quakes appear to quiet down activity on Bay area faults for several decades.

Time keeps on ticking into the future. Our fault will reawaken. My next post will look more closely at that. In the meantime, I recommend that you bookmark Temblor.net in addition to the usual sites at the U.S. and California Geological Surveys. In a Web long plagued by armwavers, alarmists and frauds, these guys are quick on their feet, know what they’re talking about and know what to say.