6.0 Quake in Napa California 1

[JAE]

Here's a couple of links:

News report

Berkley Link

USGS



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[JAE]

And a slide show of 8 photos:

Slide Show

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[JAE]

And a few more photos

Photos

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[racookpe1978]

The quake center was south of Napa, north of Vallejo, a little north of American Canyon. Mag 6 is not that big compared to what is expected up there - to what is going to be coming in the future.

When we lived there (until 1989) this area was either open land, salt marsh, wine or fields, or suburbs - one family homes 900 sq ft to 1500 sq ft, many single floor. The two and three story building were mostly light commercial (offices ) or government. Napa had one hospital that was higher, Vallejo had two others.

I'm not surprised at some damage => because many, many homes and offices were stucco over block and wood frames, but I am surprised by the amount of "shelf" goods like those photo's that were not better restrained. And, of course, the government building damages. Like the cambered up sidewalks in the slide show in the links above, most will be cosmetic. Expensive cosmetic, but not whole-scaled structural losses.

 

[TehMightyEngineer]

You would think anyone who sells wine would have some sort of rack or case system for their shelves that would prevent bottles from being slid off the shelves.

Maine EIT, Civil/Structural.

 

[concretemasonry]

Has any detailed information/statistics on the quake been released yet?

The best figures I have been able to find were on USGS and Cal Berkeley site but that was just the magnitude (6), depth of the center (7 miles), some surface settlements in deposited soil and general location of the center.

I was interested in accelerations (vertical up and down), (horizontal E-W and N-S). I got the Northridge, CA preliminary results reasonably soon but is was about a week or two after the fact and they were not too detailed at that point. Right now, all I found in searching was mention of .5G vertical at some unidentified point. The Northridge dam had a vertical acceleration of about 1.5% downward, which was a little scary.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[JAE]

Heh - I saw this photo (see attached) and recalled how many times in older buildings (and even newer ones) where I've seen the gable end of a building not very well connected to the roof diaphragm. I was in an 1890's building last year (flat roof) where the parallel roof joists were next to the exterior building wall - but not connected in any manner at all.

This is of the First Methodist church in Napa, California after the quake.

(I'm now seeing it listed as a 6.1 in the news reports)

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[mspencerpe]

I only have the news photos to go on, but it looks like the two urm structures downtown had similar modes of collapse. Second story roof near the corner. Interesting?

 

[JAE]

Found this very cool video of a quadcopter that flew around Napa filming some of the damage.

Check it out - we were thinking, as we watched it, what one of these things cost and if we could use them ourselves when
investigating structures.

https://www.youtube.com/watch?v=LQhYbfIz0n4

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[TehMightyEngineer]

My father recently got a DJI Phantom 2 Vision+ Quadcopter and has offered me the use of it with investigating structures or job sights in the future. From his description it would be more than suitable for the task and would be useful for investigating areas that would otherwise require cranes or scaffolding (or could be dangerous). I hopefully will be able to take him up on the offer sometime soon as I do a fair amount of failed structure investigations, some of which have rendered parts of the structure unsafe (power boiler explosion).

Maine EIT, Civil/Structural.

 

[TehMightyEngineer]

Cost for a DJI Phantom 2 Vision+ Quadcopter is around $1,300.

Maine EIT, Civil/Structural.

 

[wannabeSE]

JAE,
Thank you for the original links and the quadcopter video

 

[medeek]

With regards to properly restraining stuff in an earthquake prone location it really doesn't surprise me at all. People that live in these areas become complacent over time. It takes another big one for them to change their ways. Unfortunately, our building codes are somewhat similar in that respect, it usually takes lives being lost before significant changes are made.

I did an internship at IBM's Almaden Research Centre one summer and I still remember a conversation I had with one of the more senior researchers there. One of his larger vertical racks of computers was unrestrained during the Loma Prieta earthquake (1989) and the only reason it didn't completely fall over and almost injure or kill him was that he had such a tangle of BNC and CAT5 cables coming out the back of it that they somehow held it when it toppled. Of course after that incident everything in his lab was retrofitted with "earthquake brackets".

 

[oldrunner]

I read somewhere that the lateral motion was around .63g. (EERI).

There was a good study on the wine storage racks that was done by an excellent firm in SF. But that doesn't mean than anyone will do their suggestions. Remember speaking with the engineer concerning a winery I was doing in 2001 and my client wasn't interested. (In El
Dorado county).

I'm not surprised about the damage - we have a lot of URM buildings where I live - no one wants to upgrade them and the local building department gets pressured to not enforce the minimum code.

Least no one was killed in this one. An earlier quake killed a couple of women in Paso Robles a number of years ago.

 

[SteeliestFire55]

FYI, CESMD has data available from the strong motion monitoring stations. PGA was about 0.4g at the closest stations.

http://strongmotioncenter.org/cgi-bin/CESMD/iqrStationMap.pl?ID=americancanyon_24aug2014_72282711