Right Lateral, Into the Abyss of Time

We moved our family into Oakland in the late 60’s. We shopped in the Lucky Store, usually the one on Lakeshore Avenue, but occasionally we went to the Montclair store on Mountain Boulevard.

The Montclair store had a persistent problem with plumbing and damage to the floor in the meat department, which ran along the southern wall. After noticing this for several months, it occurred to me that the problem could be related to movement on the Hayward Fault, which might pass through the building.

Apparently, that was the case. The Lucky corporation decided to re-locate the store in a new building- the present site- and conducted a series of trenching studies, so they could place the new building completely on one side of the trace of the fault. The economics were such that they could take care of the persistent problem, but would not be too concerned about the long term exposure to seismic problems.

Following this process, I fully expected that the original building would be torn down. No way! It now houses the Rite Aid store. I have shopped there, just as I continue to shop at the Lucky Store. While I am aware of the hazard-shall I park in the basement or on the roof?- it does not impact my daily life.

When I was in the building, I took notice and sometimes pointed out to people, the ongoing deformation of the floor tiles. You can’t see this now as remodeling of the store covered the old floor with carpeting. I happened into the store while this remodelling process was getting started, got my camera, and took these photos of the deformed floor tiles.

Faulted Floor Tile I

Faulted Floor Tile I

Faulted Floor Tile II

Faulted Floor Tile II

The damage was confined to a zone running through the middle of the store. The floor at the entrance, and near the rear wall was undamaged.

The fault dominates the landform in the area, meaning that the basic street grid is laid out parallel and perpendicular, happenstancially, to the fault. That is, the trenchlike cleft in the landscape along which the freeway runs is the result of erosions of the shattered rock along the fault. Of course, the streets, like Mountain Boulevard, were there before the freeway, just as earlier “transportation corridors”- paths, trails, dirt roads- were their before the streets. The result of this cultural heritage is that the building the Rite Aid occupies today is oriented such that the fault slices straight through the building and the floor tiles are very close to being rectilinearly lined up.

Of course, the building structure spreads the stress and strain, so making the exact connection been fault movement and tile deformation would be pretty complicated. But the right-lateral shear (sides compressed together, opposite side sliding to the right) is nicely shown.

I don’t know the age of the building, which would tell us when the tiles were laid. Nor can I calculate the actual amount of displacement the deformed tiles represent. With these two numbers, one could calculated the movement on the fault, and compare it other studies.

Outside, on Medau Place, you can see the effects of the fault in the street.

Painted curb

Faulted Curb: Montclair

Here is a photo and a “painted” blowup  of the offset of the curb. I just took this photo a few days ago. It is across the street (Medau Place) from the building; the line of sight up the curb was better, not obscured by a refuse bin.

This site presents a different problem.
You can readily see the off-set of the curb, measureable in inches, much more than inside the store, that is across the street,to the left. Of course, the building is younger than the street. We know this from documents, and also because the building lines up with the street, which likely shows the street came before the building. So we would expect the curb to show more displacement.

But there is a problem. The curb shows a smooth bending, rather than a sharp break and displacement. We can see a break-and-slip at one place along the curb at a joint in the concrete (Actually, there are several little places along the curb, which you can see if you click on the photo and enlarge). But the majority of the off-set seems to be taken up in the smooth flex part. Rocks, and concrete is a kind of synthetic rock, can bend and flow into smooth shapes like this, but not in the environmental conditions of the Earth’s surface- not even in Oakland! Put that curb under the confining pressure of a few miles of rock, and heat it up accordingly, and it could take that form. But not on Medau Place in the 20th century.

We know how concrete is formed. It is an aggregate fluid and is poured into a form. What the bend in the curb shows is the bend in the form the concrete was poured into. So why was the concrete form bent that way? Why would they do that?

Well, there is a reasonable explanation. Curbs are laid out in relation to surveyed centerlines of streets, as are property lines. After the 1906 earthquake, it became obvious that the legal system would need to deal with the relation between property lines and moving earth. The conclusion was that property lines are displaced along faults along with the earth itself.

When the original survey of the Monclair District was done, probably in the late 1800’s, the centerline of Medeau Place was presumably a straight line, with property lines parallel. Later on, when the curb was laid out, the surveys would disclose the off-set of the centerline, and the laying out of the curve in the curb accordingly. The displacement since then can be seen in the slip at the joint.

But that means that the slip along the fault was known, or should have been known, to the builders of the Lucky Store building. Of course, they could have discounted the danger. Even such an “expert” as Andrew Lawson, in studying the 06 quake, assured the populace that they did not need to worry about any recurrence. The built up stress was dissipated. Danger would not return for many centuries, according to the then experts. It took the uncovering of the trace of the San Andreas Fault in the pit being dug for a nuclear reactor at Bodega Head to prompt a reevaluation of the theory.

From the damaged tiles to the off-set curbs we get inches of off set in perhaps a century of time. The next step is more difficult. If we had artifacts or natural structures that were formed over the last thousand years, we could work with that. But the next thing to look at here is in the range of tens of thousands of years: Palo Seco Creek.

Palo Seco Creek emerges from the groundwater in the gullies and ravines of Joaquin Miller Park, flows through those same declivities northwesterly, crosses the Hayward Fault zone and joins Shephard Creek just below the Montclair Country Club at the head of Dimond Canyon. Thence, now called Sausal Creek, the stream flows through the canyon, across the flatlands parallel to Fruitvale Avenue, and sinks underground close to the bay.

Streams crossing faults is a sport unto itself. Streams are not fixed things, and neither are active faults. Unraveling the intricacies of process and form with two dynamic processes leaves a lot or room for differences of opinion. Given that, and having walked both Dimond Canyon and Palo Seco Creek, and dined at the Montclair Country Club, even hit a few golf balls, every time I walk along Monterey Road, past the country club, creek on my right in that steep little gully, up to the cross-walk where, just as the pedestrian underpass leads under the freeway to the Joaquin Miller trails on the other side, the creek tunnels under the freeway, and borrowing some data from UC, I think of 32,000 years of displacement and what has happened in the world in that time.

Palo Seco Right Lateral

Palo Seco Right Lateral: I have "painted" the creek a darker blue in the photo of the map. I am NOT asserting that the offset has been as simple as it appears on this little map.

A roll of adding machine tape stretched out along the street between the country club entrance and the cross-walk would give us a time-line upon which we could note the significant events-significant to us.

  • Walking your dog along, the complete history of dog domestication and breeding.
  • The extinction of various large mammals in the world, including cousin Neanderthalensis.
  • The perhaps complete history of polar bears from the time of their divergence from Grizzly stock 20,000 years ago to their imminent demise due to loss of North Polar sea ice.
  • The domestication of the horse, the invention of the wheel, chariot warfare.
  • Written language- spoken language had been around a lot longer- words and numbers.
  • The retreat of the ice following the Last Glacial Maximum. The subsequent diversification of at least the northern races of humans who followed the retreating ice.

I don’t want to give the impression that I am attempting to prioritize this listing. They are just things that happen to come into my conscious mind as I write this. Obviously, except for the landscape, the world of 32,000 years ago would be frighteningly different from today. I can walk this route today while thinking about getting something to eat without worrying about what other creature might be on the path, perhaps a not-very-Golden-Bear grizzly bear, with the same motivation but with me as a target!

The mind does indeed grow giddy, looking only a little way into the abyss of time, while staring at some damaged floor tiles in a drug store.


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