The Wild Oakland walk on the Hayward fault

9 November 2014

Saturday I led a walk for the members and friends of Wild Oakland to show off one of Oakland’s most striking places to encounter the Hayward fault. There was a nice turnout, about 60 people. I was glad to see so much interest. I hope that this post will enable those people, as well as all of you readers, to visit in person and learn more.

Here’s the route we took. It was just over 3 miles, although the altitude gain in the middle made some people bail out. Next time I’ll try to have alternative routes for their benefit.

WildOakwalkmap

The numbers refer to the stops during the walk. The asterisks refer to direct evidence of the fault’s activity, both on and off the day’s route.

Next is the same map with topography added. The thrust of the day’s exercise was to tour some distinctive features that the Hayward fault has left on the landscape.

WildOakwalkmapterrain

Stop 1, where we started, is where Arroyo Viejo does its abrupt 90-degree turn on its way from the hills to the bay. The right-lateral Hayward fault has dragged the Bay side of the landscape to the northwest, and the creek has had to bend in response.

WildOakwalk11-14-1

It’s a vivid example of how plate tectonics works in California, caught between the Pacific and North America plates. As the Pacific plate moves northwestward, pulled in that direction by subduction zones off Japan and Siberia and Alaska, it moves sideways—right-laterally—with respect to North America. That distorts the courses of streams that cross the boundary between the two plates. That plate boundary is a wide zone with three main sets of major faults running along it. The Hayward fault is in the middle set.

At Stop 2 I was able to point out a good example of creep offset, where the curbs on both sides of Encina Avenue have been cracked and shifted by creep (slow motion, less than 10 millimeters per year, without earthquakes) on the fault.

WildOakwalk11-14-2

Stop 3 gave us a decent elevated view of the fault zone from the Oakland Zoo grounds through that offset valley of Arroyo Viejo. (Here’s an earlier post showing the other direction.)

At Stop 4 I pointed out another probable example of creep offset, and everybody turned on cue to look at it.

WildOakwalk11-14-3

Stop 5 was at a highly disturbed bit of ground on Ney Avenue. The scarp crossing the road appears to be the head of a landslide right on the active trace of the fault.

WildOakwalk11-14-3a

Stop 6 was on a hilltop in the King Estates Open Space with a high view over the fault zone and the rest of the Bay area. The set of smooth-topped ridges extending into the valley of Arroyo Viejo have been cut off to form shoulders, and the dramatic shutter ridge on the right is the landform that has forced the stream to run sideways around it instead of straight to the Bay as it would prefer. (Here’s an earlier post about this same view.)

WildOakwalk11-14-4

I am quite taken with King Estates, and I believe it to be the largest piece left of the East Bay hills’ original landscape of grasslands. As the rains come this winter, I hope some Wild Oaklanders will poke around and examine it closely. For most or all of the people who came, it was their first visit.

click for 900-pixel version

Along the way is this nice little example of a landslide.

WildOakwalk11-14-5

The King Estates hills are mapped as alluvium of an earlier generation than the Pleistocene alluvium that makes up East Oakland’s low hills. I wonder two things about them. Are they a pressure ridge, pushed up by compression across the Hayward fault? (I noted that the fault’s motion is 90 percent strike-slip and 10 percent compression.) And what is to be learned from the blend of stones that practically forms a pavement on the hills?

WildOakwalk11-14-6

Stop 7 was a view into the watersheds of the three creeks above the fault: Rifle Range Branch, Country Club Branch, and Arroyo Viejo. And Stop 8 was in the valley of Country Club Branch, so close to its neighboring streams but so well separated from them by elevated divides. I blame the fault, which keeps jolting the countryside out of the equilibrium it seeks.

For dessert, I present a portion of Jim Lienkaemper’s 1992 map of the fault, which has annotations about the detailed evidence along it.

WildOakwalk11-14-features

The features marked G are geomorphic—things geologists notice in the landscape. Those marked C are hard evidence of creep—offset curbs (rc), sidewalks (rs) and fences (rf), and at Stop 2, echelon cracks (ec) across the road that have been erased by road repairs since 1991 when the map was compiled. You can download the whole map and consult the updated version from 2008 if you like.

Geological issues in the 2014 election

31 October 2014

Nobody asked for my guidance in this fall’s elections. That’s OK—this isn’t guidance, just a few observations from October.

The mayoral candidates in Oakland, almost unanimously, have ignored the two geological elephants in the room. First is the Hayward fault and its chronic threat to this wonderful city. Oakland is the upcoming victim, at some time unforeseen, of a magnitude-7 earthquake that will rip the ground all the way from beyond Sheffield Village to beyond the Claremont Resort. And ten times as many magnitude-6 events, the size of the 24 August Napa earthquake, will arise from the same stretch of the fault in the next century or so. Second is the rising sea level, which within our children’s lifespans will lap onto the waterfront and airport.

But those aren’t really election issues; they’re policy issues. We have staff making plans and pushing them forward an inch at a time, about as fast as the Hayward fault creeps. I’m sure that our next mayor, whoever it is, will support them fully. One of those plans is aimed at our large stock of vulnerable buildings—soft-story apartments. These multifamily dwellings, many of them fine old buildings, house some 20,000 people. In forecasts of the Big One, fully two-thirds of the Oakland residents made homeless will come from this class of structure. The city has mapped them, and when you contemplate the map maybe you’ll start thinking of them the way fire officials think of old-growth eucalyptus stands.

oaklandsoftstorymap

The Oakland Soft Story program has made good progress this year. Mayor Quan and Councilor Kalb got a task force together in April to get an ordinance ready for early 2015 that will concentrate on this low-hanging fruit of civic resilience, and I commend them both. (City Manager Henry Gardner published an excellent memo this month on the status of the program.) Dan Kalb isn’t up for re-election this year; Jean Quan is. Quan also is the only one of the mayoral candidates to mention earthquakes on their websites. She has a lot going for her, from my parochial viewpoint, like her support for the geology sign at Joaquin Miller Park. She took the time to show up at the Loma Prieta 25 policy conference on October 16, where she presented a spirited defense of the city’s earthquake preparedness efforts.

She gets it. I didn’t vote for her, though, because I think at least three other candidates will make better mayors. It’s OK if you disagree about that. But I trust that all of the likely winners will carry on correctly, with goading from Dan Kalb and skilled assistance from our Chief Resilience Officer, Victoria Salinas. Both of them get it, too.

That’s earthquake preparedness. Nobody’s talking about sea-level rise, but a lot of people are thinking about it, and I believe we’ll make the necessary adjustments in a timely way. It happens that the subject is on Salinas’s radar. If you never heard of her before, it’s because the Chief Resilience Officer is a grant-funded position that just started this year. I very much want her to succeed and be supported here after the grant runs out. Again, not an election issue.

On the state side of the election, I have less to say. The big water bond, Proposition 1, will direct some money at the Delta levees, which is an enormous area of vulnerability to earthquakes and sea-level rise. The more money the better, I say.

And in the Secretary of State election, I believe in Alex Padilla. He was off my radar until he sponsored the legislation for the statewide Earthquake Early Warning network last year. And last month at the Third International Earthquake Early Warning Conference, he showed up and seemed quite at home among the scientists and emergency-response people who care deeply about this technology. Turns out he’s a trained mechanical engineer, and as state senator for the district including Caltech, he regularly visited the school to keep up with the science there. It was by chance during one such visit that he got wind of the ShakeAlert early-warning system, and to his credit he took up the issue and carried it over the goal line. I believe that as Secretary of State, he would do the right things for the state’s voting technology. Actually I’m sure Pete Peterson would do a good job too, but I want to reward Padilla for good behavior even if he never deals with earthquake stuff again.

BTW check the Announcements/Q&A page about a walk I’ll be leading on November 8.

Penjing—in Oakland?

25 October 2014

Havenscourt Boulevard is a handsome street—wide, with a row of large palms up one side and offering nice views of the Seminary gap and the low and high hills. Then there are the homes, where I spotted this creative use of a roof drain.

penjing-havenscourt2

The water runs down a chute to a stilling basin, where it gently wells over the rim and waters the lawn. And the structure is outfitted with miniature buildings and picturesque rocks in a nice example of the Chinese art of penjing.

penjing-havenscourt

Penjing is related to the Japanese art of suiseki, but is not as abstract. Instead of suggesting ideal forms through the prism of naturally formed stones, penjing uses stones and models to depict landscapes, more or less fantastic, in miniature scale. It can range from kitschy to sublime. This example is what I would call homey, and very Oakland.

Loma Prieta plus 25

17 October 2014

Yesterday I attended the Loma Prieta 25 Symposium at the Kaiser Center. It was a quake geek’s Woodstock, where a motley host of experts got together to schmooze, celebrate 25 years of progress since the 1989 earthquake, and look ahead. At 10:16 a.m., along with 27 million other people around the world, we participated in the ShakeOut drill.

dropcoverhold

Since the Loma Prieta earthquake, Caltrans has finished reinforcing all of the state’s freeway overpasses, EBMUD and Hetch Hetchy have strengthened their principal water mains where they cross the Hayward fault, BART has strengthened its tracks and stations, and PG&E has made huge changes to make the power and gas system more robust. The airports and ports have been upgraded. The big bridges have been fixed or replaced (with only the Golden Gate Bridge upgrade to go).

The work done since Loma Prieta has also made governments work better. The mayor of Napa, Jill Techel, had high praise for the city, county and state emergency service agencies. She said PG&E did a wonderful job during the August earthquake. The federal agency FEMA was on top of things too. And the regional authority ABAG, the main sponsor of the symposium, was charged with energy and ideas to piggyback on the public awareness that followed the Napa quake.

Magnitude-6 events like the Napa earthquake will happen 10 times as often as the “big ones” we’re warned against. Even if the big ones will surely overwhelm some aspect of our preparations, the mitigation and preparedness in place can work wonders with the smaller events like the Napa quake.

The next steps that the experts laid out, the things they want done by Loma Prieta 50, involve increasing the Bay area’s resilience to disasters. Resilience means that people will not just avoid death and injury from a major earthquake, they’ll stay in their homes and return to their jobs quickly. The work of upgrading the infrastructure needs to move beyond the backbones to the limbs and arteries: neighborhood water and gas lines, smaller bridges, individual privately owned buildings. Oakland is ready to begin a program aimed at some 1800 soft-story residences in the city. The state’s earthquake insurance chief and the state senator heading the Insurance Committee were there to describe the advances they want to make in 2015. Progress works this way: inch by inch and year by year.

Emeryville

9 October 2014

The little town of Emeryville has almost no geology that passers-by would recognize. On the geologic map it’s displayed as largely artificial land and coastal alluvium.

emeryvillemap

The only people who see these things are builders and the geological professionals who advise them with their foundations.

The point was made from scratch—the original shore was a straight line pretty much where the railroad is now. Out at the end it’s been prettied up into Marina Park, a simulacrum of a wooded meadow. I like it there.

e-ville-point

A seawall, made of typical Franciscan riprap, protects it from the mild surf that manages to get here through the Golden Gate.

marinapark

The park-y part of Marina Park offers great views of Berkeley and points north. This is a good place to test your knowledge of the geography: Can you point out Strawberry Canyon, for instance. The highest point in this picture is Grizzly Peak.

e-ville-sculpture

We aren’t making any more artificial land in the Bay area, thank goodness. For a while there, people were planning to fill the whole Bay in. The nice thing about artificial land is that we can feel free to decorate it, whether formally as here or informally as at the Albany Bulb.

The Las Aromas serpentinite

26 September 2014

The southern edge of the Piedmont Pines neighborhood butts against Joaquin Miller Park, and there’s no reason to visit if you don’t happen to live there—except if you like serpentinite. The street named Las Aromas dips into the belt of serpentinite that extends up and over the ridge to Serpentine Prairie, and the rock type is well exposed. One resident has done a lot of landscaping in this inhospitable rock type.

lasaromas-serp1

The scaly structure is typical of serpentinite, and here it’s fairly close to the Hayward fault. Farther uphill is this exposure, where the grain of the rock is parallel to the street.

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Its blue-green color is striking. And there are a few spots where friction in the recent geologic past has turned it glossy. The rocks aren’t as spectacular as Serpentine Prairie itself, but they’re still noteworthy.

lasaromas-serp3

I never tire of our state rock. Speaking of Serpentine Prairie, today on KQED Science there’s a story on the ongoing effort to propagate the rare Presidio Clarkia. (I photographed it a few years ago before they fenced off the area.)

After Oakland’s Big One, expect a rush of water

8 September 2014

In the days since the South Napa earthquake of 24 August, the people and press appear to be astonished as the local streams have filled with water. The Chronicle published a good summary yesterday. But this always happens with a decent-sized earthquake. It will happen here. You can expect to see this stretch of Arroyo Viejo, in the middle of Hegenberger Expressway, full of freshly released groundwater.

hegenstream

There were widespread reports of this kind in 1857, after the the great Fort Tejon earthquake of 9 January:

On a range of hills, about fifteen miles from the coast, in the district of San Fernando, we understand that a surveying party have discovered quite a large stream making out of the mountain and down a cañon, where, to their knowledge and complete satisfaction, not to say to their sorrow, no water was running or could be found previous to the earthquake. By the letter from Tejón, it will be seen that a similar circumstance occurred in that vicinity. Los Angeles Star, 17 January 1857

Just back of my camp was the dry bed of a stream, where in heavy rains water had at one time run; in this bed two weeks before I had sunk a well some 20 feet hoping to find water, but at that depth the earth was so dry I gave it up as fruitless. Two days after the first or heavy shock a little stream of muddy water was running by my camp which continued to increase each day, until when we moved was quite a little rivulet: no doubt the result of some new fissure in the mountain. Letter of W. E. Greenwell, U.S. Coast Survey, 24 February 1857

The effect upon some of the artesian wells in this neighborhood was remarkable: for a moment the water ceased to flow from the pipes, and then gushed out in greater volume and with more power than usual; we have heard that the channels of other wells, which had become obstructed, and ceased to discharge water, have become re-opened and the subterranean current is now flowing out from the orifice. San Jose Telegraph, 13 January 1857

The water goes away after a few weeks. UCB geologist Michael Manga explained the phenomenon in a talk I attended in May of last year: The shaking settles the bedrock, which in turn forces the groundwater it contains upward. In effect, the rock’s permeability in the vertical direction increases as a result of basement consolidation. This is the same basic mechanism that creates quicksand. Studies after the 1999 Taiwan (Chi-Chi) earthquake showed that this water would be replaced in about 140 years—which is coincidentally the average interval between large quakes on the Hayward fault in the last thousand years. The effect takes place within a rupture length of the fault—that accounts for the response of wells in San Jose to a Southern California earthquake whose rupture ran about 360 kilometers, from Parkfield to Cajon Pass.


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