News from the HayWired fault

16 April 2018


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.

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Land and rocks of westernmost Piedmont

2 April 2018

The western end of Piedmont includes the headwaters of Pleasant Valley Creek, which is tucked under Grand Avenue. But the slopes and gullies of the valley can’t be hidden, and what may seem like a scramble of streets is a nice place to walk around. The topography I’m talking about is north of Oakland Avenue, between Grand and the former quarry of Dracena Park.

None of it’s bedrock; nothing wrong with that. It’s the uppermost part of lobe 3 of the Fan, that big arc of ancient alluvium hills across central Oakland. The bedrock part, farther uphill, is much steeper walking, and the rock (the blue field labeled “Kfn” on the geologic map) doesn’t show itself either.

I should make an exception to that statement — Dracena Park is a great place to see the bedrock. But for the purposes of this post it’s just a pretty place, either in the former main pit:

or in the valley on the north side, now full of redwoods.

This is the most dramatic bit of stream valley in the area. Elsewhere, it’s easy to trace the drainage lines; in fact during our recent batch of rain, you could see water coming out of the ground just like in the old days before people lived up here.

This slopy bit of suburbia is criss-crossed with hidden history. The Key System streetcars used to serve the neighborhood. Indeed, a railroad syndicate once planned a major route through here that was going to run through upper Fruitvale and on to San Jose. The right-of-way appears in this 1927 map (courtesy of the Oakland Library History Room), long after the plans were abandoned.

The part of it running as far as Oakland Avenue did end up with rails as part of the Key System’s C line. If you look closely at the area in Google Maps, the lot lines give the route away.

The transit routes, road and rail, took advantage of the saddle in the ridge of lobe 3, at this spot where Pleasant Valley Road eases over the hill and becomes Grand Avenue. The view is west across the saddle toward Rose Street.

OK, enough of that. There are indeed rocks in this neighborhood. See that clever stone wall in the foreground in the previous shot? Here’s a closeup.

Other rocks are more laid back, understated but cool.

Still others, the only word for them is homey.

They’re all mostly landscapers’ stone, purchased at a commercial yard. But here and there you’ll see genuine domestic Oakland rocks. This little wall is made of serpentine/blueschist from around here, probably the pit at Serpentine Prairie or nearby.

And the Franciscan red chert is very likely from Piedmont itself, which sits on a hill of melange, a marble-cake rock unit that mixes chert, basalt, sandstone and serpentine in a mudstone matrix.

Some of it can be downright psychedelic. Stuff like this was quarried in Piedmont before any buildings were here at all.

Even the sidewalks, the oldest ones anyway, incorporated aggregate from Piedmont’s original quarries.

The town has grown up since then. It puts on a good front — very nice homes, lovely grounds, a fine place for walking and taking in the views (especially when the leaves are down in winter). But it began as a rugged, dusty mining district with horses and dynamite.

Oakland geology ramble 5: Grass Valley

19 March 2018

Over the last few weeks I’ve been exploring the remote land just east of Skyline Boulevard, over the city line in Anthony Chabot Regional Park. Time to show you some of the charming features of Grass Valley, seen here from Redwood Ridge near the Parkridge land bridge.

In classic Geology Ramble style, this walk (a set of them actually) starts at one bus stop and ends at another. It starts at the top end of the 39 line and ends at the top of the 46L. The challenge is that you can only do this on weekdays because neither line runs on weekends; moreover both lines only run once an hour. Here are the two routes I’ve done so far, in the Google Maps terrain view just to give a feel for the territory (800 x 100 pixels). There are 12 photos in this post, locations given in a map at the end.

The route on the right runs down Redwood Ridge, and the first part is just like what I showed you last month only more so. Where it meets the other route, at the Bort Meadow staging area, you get this view of the valley floor. You can see it looks completely different in cloudy weather. Without the distant views across the Bay and south into the Diablo Range, it’s intimate and secluded. (The rest of my photos are from the western route.)

Amelia Sue Marshall, in her new book East Bay Hills, a Brief History, says that Grass Valley was never settled by whites or Ohlone because the stream was unreliable. Back in the day, redwood lumber was hauled through the valley to Castro Valley; only a few redwoods actually grew there. Later, cattle were driven through it between Oakland and Moraga. The Grass Valley Ranch raised cattle there for many years until the water companies moved in. The East Bay Water Company and the Contra Costa Water Company both planted huge eucalyptus forests there, and finally East Bay MUD took them all over. When they secured Sierra Nevada water, their East Bay land was transferred to the East Bay Regional Parks District, and that’s the story.

The ramble starts at Skyline High School. The scenic way is up the median path of Skyline Boulevard, charming in all seasons. It also exposes the Oakland Conglomerate, as I’ve posted previously.

The road up to the city stables is marked by a sign. Go past the gate and enter the Goldenrod Trail, an old dirt road popular with horse riders. It’s pretty, and you’ll see outcrops of Oakland Conglomerate along the way.

You knew I’d get to the rocks. The gross terrain is shaped by the rocks beneath it, but not much rock is actually exposed. These rocks began as sediment, and to sediment they quietly return, mostly covering themselves in a forested blanket of soil.

The important map units are Ko, Oakland Conglomerate; Ksc, Shephard Creek Formation (mostly shale); Kr, Redwood Canyon Formation (mostly sandstone). Grass Valley is strongly confined by the shale. The upper slope, though, is conglomerate. You can usually tell by the well-rounded stones embedded in it — samples of ancient mountain ranges. They get as big as this.

And there’s more than rocks to shake a camera at. For instance, banana slugs.

Take the Ranch Trail or the Buckeye Trail down into the valley. Near the bottom the woods open up nicely.

After a while you reach Bort Meadow. A hundred years ago the water company called it the Big Trees area, but the park took down most of the eucalyptus and it’s much better now.

The stream gradient is very gentle; this area looks like it could have been a lake at various times in the recent geologic past, especially if landslides dammed it.

Grass Valley is still a ranchy, horsy, countrified place. Though it’s gone from drivin’ dogies to walkin’ doggies.

The first time I came through the valley, unsure of my pace relative to the bus schedule, I was trotting. After that I knew I could amble instead. The whole hike is less than 6 miles, and the climbs aren’t that strenuous.

Farther down the woods rise up and close in, first oak and then eucalyptus.

By the time you reach the Stone Bridge the woods are thick. I haven’t yet gone farther toward Lake Chabot; the public transit logistics are pretty daunting. Take a minute to look at the streambed above the bridge; the Shephard Creek Formation is well exposed there, but look from afar because the creek bed is fenced off as sensitive habitat.

From the bridge turn up the Jackson Grade, where you’ll meet the bottom end of Skyline Boulevard. (There’s a water faucet at the top of the grade.) From there it’s a quick downhill into the Grass Valley neighborhood. The eucalyptus allee on Grass Valley Road is pretty to look at, harrowing to drive and inadvisable to walk.

Instead, cut over to Scotia and down Shetland and contemplate the classic postwar burbia around you as you head for the bus stop.

As promised, here’s the photo key.

You could take this route the other way, but it’s uphill, from about 500 to about 1100 feet.

A new kind of shoreline

5 March 2018

Rising sea level is a threat to the Bay area. Already, king tides are flooding the levees and seawalls built for the last century’s ocean. I touched upon this topic a few weeks ago with my proposed walk around Lake Merritt in 2100, assuming that the Bay will be a couple meters higher than today.

Yesterday, happenstance allowed me to witness a promising project that has built an experimental coastline modeled after a natural one — specifically, a living water filter meant to sit between the low tidal mudflats and the higher levees holding the Bay back. The Northern California Science Writers Association arranged for a group of members to visit the Horizontal Levee Project, on the grounds of the Oro Loma Sanitary District wastewater treatment plant in San Lorenzo.

Let me sketch the idea behind the project. To begin with, the natural coastal landscape has been totally messed up. It used to be a nice grassland plain, gradually sloping down to a series of wetlands that merged organically into the tidal marsh, mudflats and open Bay waters. Water from the hills percolated gently down the streams and through the ground, nourishing a lovely ecosystem full of species. American settlers cut off the top part of this landscape and covered it with buildings, dammed and diverted the streams, then filled in and walled off the lower part with levees. Today the coastal wetlands are cut off from the water and sediment from the hills, and meanwhile the sea is creeping up and washing them away.

The thinking behind the Horizontal Levee Project is to build a new slope on the uphill side of this truncated coast, then restore the groundwater flow that used to be there using treated wastewater. Even compressed to a fraction of its former width, the resulting slope should be a powerful water-scrubbing engine and a vibrant habitat. (Figure from here.)

The wastewater part is crucial because we have lots of it, we can control its flow, and the new slope — scientifically, an ecotone — cleanses the wastewater of nitrates and other hard-to-remove compounds better than treatments costing 10 times as much. All while feeding a splendid tidal marsh that resists storm waves better than concrete walls!

Our visit took place on a brisk, bright day by the bayshore. The Oro Loma Sanitary District treatment plant is mostly clean, stark and Brobdingnagian.

But the operators found space to put up this pilot project on their own land, where they didn’t need so many permits. They built a gently sloping earthwork, installed pipes at the top and drains at the bottom, then raised a mix of plants from local sources to seed it with, using these planter boxes.

Project staff noted that the alkali bulrush is particularly good at resisting storm waves with its tall, stiff stems.

Seeding and planting happened in the rainy season of 2015-16, so this lush jungle of native marsh plants on the ecotone was just two years old. It’s so dense that invasive weeds, even pampas grass, don’t stand a chance.

And the water coming out at the lower end is really clean. (Even so, the water was pumped out through the white pipes on the left and put back into the treatment stream.) Soil bacteria actually convert the nasty nitrate to nitrogen gas, so it isn’t just trapped in the dirt or building up within the plants.

Water treatment agencies all around the Bay have their eyes on this experiment. It looks like the design will be flexible enough to be adapted for as much as 5000 acres of wetlands, a significant fraction of the coastline that’s particularly vulnerable to sea rise.

Awareness of sea-level rise needs to happen faster than the rising sea itself. The speakers yesterday found that the hardest nut to crack in moving things forward is regulations: interpreting them creatively, coordinating the regulators, combating inertia. To envision, scope, design and plan improvements to the shoreline literally takes decades, meaning that we have to aim for a target in the year our children reach our age.