LA Earthquake Risk

Steve Sailer writes:

This bill, at least in its original form, would have legalized a lot of 8-story buildings along Ventura Blvd. in the SF Valley, which might be a good idea, except much of the north side of Ventura is built on the old LA River floodplain of sand and gravel, which liquefies during an earthquake.

After the 1994 Northridge earthquake, my dad took a map of all the condemned building in the San Fernando Valley and showed that about 80% of them were built on the old dry riverbeds, which only make up about 10 or 20% of the land of the Valley.

The government has, very slowly, mapped the type of soil and thus the earthquake risk in LA block by block, but the real estate business doesn’t want to think about it. And the real estate professionals do a lot of thinking for people these days, so not many people think about it.

…In this map, the entire southern portion of the San Fernando Valley is likely to liquefy in an earthquake. SB 827 would have turned most of that area into eligible for 8 story apartments.

But some parts are even worse than others. Many apartment buildings on the south side of Moorpark fell down in 1994 but fewer on the north side of the street because the street was originally built on the north bank of the LA River flood channel. So the south side of the street buildings built on sand and gravel performed worse than the north side buildings built on clay or whatever is the soil.

I presume that over the millennia, the flood channels moved around all over the south side of the SFV, much like how the LA River used to exit into the Pacific at Marina Del Rey up until 1825 when it moved 20 miles south to the current LA Harbor. But, probably, the more recent flood channels are worse building sites…

The San Fernando Valley has a lot of pretty standardized construction, so where building were hit hardest in 1994 is a pretty good test of the underlying soil.

In retrospect, the government should have bought up the hardest hit parts and turned them into parks and the like. The LA River restoration idea could have used land for flood control for the raging river to spread out into, which would be the same sand/gravel land that liquefied in 1994.

The real estate downturn of the mid-1990s would have been an ideal time for that.

My suspicion is that real estate interests persuaded government scientists to rank huge areas on a simple yes-no scale rather than on a bad-worse-worst scale. So now real estate salespeople can say, yeah, sure, the whole southside of the Valley is kinda bad, but whaddaya gonna do? Buy in the _north_ Valley?

* “California’s once-unrivalled status as the country’s most educated state has long since disintegrated under the waves of low-skilled, low-social-capital Mexican and Central American immigrants. Now, California’s K-12 system rivals Mississippi and Alabama as an education backwater. The state’s school-age population, now majority Hispanic, lacks competitive linguistic and math skills. California is becoming another Brazil, divided between fabulously wealthy elites hunkered down in their own coastal sanctuaries, and a poor, Third World population.” – Heather Mac Donald

About Luke Ford

I've written five books (see My work has been followed by the New York Times, the Los Angeles Times, and 60 Minutes. I teach Alexander Technique in Beverly Hills (
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