San Fernando Valley cityscapes: An example of the benefits of fractal devastation?

I know we have some readers in the L.A. area and you might be interested in a comment on our recent post regarding the beneficial (in a Jane Jacobs sense) effects of selective devastation of micro-neighborhoods in a city. I gave the example of London after the fractal effects of bombing in WW2, and BMGM wrote:

I have another case study for you.

The Northridge earthquake knocked out a great many apartment buildings in the San Fernando Valley (SFV part of LA) in 1994. Destruction was uneven for several reasons. “Soft story” buildings were particularly vulnerable and that type of design was common in small apartment complexes. The waves reflected off the nearby granite mountain ranges and formed an interference pattern across the alluvial plain/valley. This caused scattered destruction over a wide area.

The SFV has enjoyed a renaissance after the quake. It’s residents enjoy some of the highest Walkscores in California–comparable to San Francisco. I would really like to see a study that compares the economies and demographics before and after the earthquake and compare that with mega development.

I’d like to see that study too. It’s truly a natural experiment.

15 thoughts on “San Fernando Valley cityscapes: An example of the benefits of fractal devastation?

  1. There’s a much simpler explanation for the main pattern of destruction from the 1994 Northridge earthquake than “interference,” which my father discovered by plotting old river washes atop a map of condemned buildings in the San Fernando Valley: as the Bible says, a house built on sand cannot stand. About 80% of the uninhabitable residences were built on what used to be the sand and gravel beds of the Los Angeles River and its tributaries.

    In the San Fernando Valley, the typical streambed was about a quarter of a mile wide and virtually dry year round, except during roaring floods. After the destructive 1938 floods, the Army Corp of Engineers built giant concrete ditches for the Los Angeles River and its tributaries. This allowed apartments and homes to be built on the sand/gravel base right up to the edge of the concrete ditches. These sandy margins shook harder in the 1994 quake than the rest of the Valley, which is more compacted soil. For example, Moorpark St. in Sherman Oaks lies on the edge of the old streambed. Few apartment buildings on the north side of the street, away from the Los Angeles River, collapsed, but many apartment buildings on the south side of the street, built on riverbed sand, shook harder and collapsed.

    (Similarly, in 1994, Santa Monica was hit bad despite being relatively far away from the epicenter because much of it is built on the old bed of the Los Angeles river that ran west to Marina Del Rey before the flood of 1825 rerouted it south to the Harbor. This is much like the Loma Prieto earthquake in Northern California during the 1989 World Series that did much of its damage 60 miles from the epicenter in the Marina district, which is built on landfill. The word used by earthquake geologists for the extra-strong shaking of sand/gravel is “liquefy.”)

    The smart thing to do would have been for the government to use the low real estate prices after the earthquake to buy up especially shaky ground and turn it into parks, but almost nobody noticed the pattern besides my father and it would have cost money and there is a lot of property owners who want the danger of their real estate to be swept under the rug. So, this wasn’t done.

    • Following the Bible analogy one might plot the locations of the porn industry against the destruction to fine evidence of divine intervention.

      “The house of the wicked shall be overthrown; But the tent of the upright shall flourish.” Proverbs 14:11 (ASV)

      • +1

        I don’t know if just offhand mentioning “my dad has a simpler explanation” is a good reason to overthrow a scientific study’s conclusion, if interference indeed was their conclusion.

        • It’s more complicated than that, the soft sediments slow the waves and this causes the waves to have higher energy density there, it also affects the scattering of the waves and soforth leading to interference patterns so really it’s not a different explanation, just one of the factors that influences interference patterns.

  2. From a statistical modeling point of view, the large “neighborhoods” shown on the map above are too coarse-grained to examine the effects of the 1994 earthquake.

    (By the way, most of the neighborhoods of the SFV are simply post office designations within the vast city of Los Angeles. On the other hand, Burbank and a few other places are legally separate cities. And, finally, Tarzana is indeed named after Tarzan in honor of local resident Edgar Rice Burroughs.)

    Although Northridge was hit pretty hard in general, destruction tended to be quite localized, following old river beds. For example, the east-west Ventura Boulevard, the main commercial drag, parallels the Los Angeles River, so shops and restaurants along Ventura were hit hard economically as nearby residents had to move out for home repairs and cut back on dining and boutique shopping for awhile. But the effect was probably over in a couple of years.

    Hard hit micro-regions like the south side of Moorpark St. just north of the LA River where many apartment buildings dropped into their basement parking garages (the death toll was surprisingly small because most residents were in bed at 4 am and their mattresses cushioned their 9 foot falls) were typically rebuilt with apartment buildings of slightly larger size. So the main effect was probably rents going up as tired 1950s buildings were destroyed and replaced by posher 1990s buildings.

  3. “The SFV has enjoyed a renaissance after the quake. It’s residents enjoy some of the highest Walkscores in California–comparable to San Francisco.”

    In general, if Walkscores rates the San Fernando Valley comparable to San Francisco in walkability, then there is something wrong with the metric.

    The Valley has, by suburban standards, very small lots — mine is 1/6th of an acre — so it’s not that long of a haul to amenities, but there aren’t that many amenities. Most of the Valley north of the prosperous southern edge suffers from a lack of any place in particular to walk to. The closing of video stores hasn’t helped, since they provided a destination within reach of a stroll. I live within walking distance of a major bookstore on Ventura Blvd., so I walk there several times per week, but that’s pretty rare.

  4. In general, Jane Jacobs’ theories don’t work very well in the modern San Fernando Valley, where simple demographics dominate.

    The main change over the last half century is that the Valley has become much more fractured by class along ethnic lines. When I was a kid, the Valley was the promised land of the common man, so there was a fairly wide range of young white families from upper working class to upper middle class. Another Valley Dude, Benjamin Schwarz of The Atlantic, has written beautifully about that era:

    Proposition 13 has allowed many older residents to hang on to their homes by keeping their property taxes from shooting up. But the apartment blocks north of, say, Burbank Boulevard are largely Latino. Hence, younger white and Asian families below the upper middle class have been largely squeezed out by demographic changes in the Los Angeles Unified School District, which is now less than 10% white.

    When I was a kid in the 1960s and 1970s, it was a point of ideological pride among the many Jewish kids in my Valley neighborhood (which was basically the slums of Beverly Hills) to attend public school. They looked upon us Catholic school kids as vaguely un-American. Now, the neighborhood is full of private Jewish day schools.

    Until the 2010 election, the Valley was represented by Howard Berman and Brad Sherman in Congress, both Jewish Democrats. It took some heroic gerrymandering by Berman’s brother after the 2000 Census to keep a Mexican district from being created in the Valley. Finally, the 2010 Census led to the Mexicans getting their own Congressperson, and Berman and Sherman had to battle for the remaining white seat, with Berman losing a very expensive election in 2012.

    In the modern Valley, if you are white or Asian and can’t afford private school tuition and can’t wheedle your kid into one of the elite programs within the LAUSD, you generally move out of town or don’t have kids at all.

    So, there is today a larger racial gap in many ways between whites and Latinos in the San Fernando Valley than in the 1970s. Almost all the younger white families are quite affluent, and frequently connected with the entertainment industry. They tend to live near the southern edge of the Valley and look upon the rest of the Valley as a tacky Latino cultural wasteland.

    That’s something of a caricature, due to Proposition 13 allowing some young families to inherit homes in the rest of the Valley from their parents. (That Proposition 13 has kept the Valley somewhat integrated is seldom discussed since Prop 13 is such a hate icon to liberals.)

    Much of the demographic change in recent years seems to be the result of ex-Soviet Empire or ex-Ottoman Empire residents moving into the central Valley, following the lead of the Armenians who started arriving in the mid-1970s and promptly started racial brawls with Mexicans at Grant H.S.

    The Armenians in Valley Glen don’t find Mexicans much to worry about. The Armenians just build vicious-looking fences around their yards and glare at any Mexicans walking down their streets. Russians, Israelis, Iranians, Ukrainians, and others from Eastern Europe and the Middle East have been following the Armenian example. So, my guess is that in the very long run, Latinos will be pushed out of large sections of the Valley by new, tougher white people from Eurasia.

  5. I learned about the interference patterns from NIST scientist and University of Colorado physics professor, Judah Levine. (I was a graduate student at the Joint Institute of Laboratory Astrophysics, where he taught.)

    Judah has had an amazing career, starting out in public housing and developing precision timing techniques for delivering time over the internet and for Navstar/GPS. One application of precision timing is in locating earthquake origins and distinguishing earthquakes from underground nuclear testing.

    After the Northridge quake, he served on a special commission to study the causes of the destruction and how to mitigate risk in the future. He found the interference patterns so remarkable, he spent a whole lunch period telling me about them. The commission concluded that it would be really difficult to engineer for the maximum forces experienced by buildings that land in the bullseye. The locations of the bullseyes will vary by location of the original rupture and the orientation of the waves relative to the mountain ranges. This was something that really worried him.

    I wasn’t privy to the detailed data he saw. (I have served on other government commissions in the past and, while the reports are public, the data is often not.) I do know that he is a very careful scientist and would have controlled for stream beds. Heck, this guy even controls for incident sunlight on the laboratory building and the thermal expansion of the sunny side vs. the shady side. This caused the lab to “bend”.

    He was talking about how one block would be fine, and the next one would be flattened. When they mapped them out, they saw definite interference patterns that agree with ground motion models.

    Some pockets of SFV enjoy very high walkscores, but they are embedded in a reddish field. Note that SF has pockets of red in a greenish field. I was referring to the micro level, not the macro.
    Check out some of the green (most walkable) hotspots of SFV, particularly along Ventura Blvd.

      • Yeah, but there’s a long way between “different sizes” and “self-similarity at all (or very many) length scales”. For example, if the interference explanation is correct there is an intrinsic length scale in the problem. The situation would look chaotic (in the sense of laser speckle) but it wouldn’t be fractal. I don’t know whether the result of a WWII aerial bombing campaign is close to fractal, but its not obvious to me.

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