A reader asks: “In on-going construction, should there be any concern about the effects of the recent minor earthquakes? Are uncompleted projects more vulnerable to shifting/etc.? Is there any sort of assessment that is done after such an event to ensure integrity? Thanks for any insight!”
We’ll have to echo that “thanks for any insight.” Readers?
Most modern construction around here aims to withstand a 7.0 quake or greater which are many many times more powerful than the ones we just had. So it’s unlikely that those recent quakes did damage to any type of construction. As for new construction, it’s built structural elements first (including those that protect against earthquakes like the foundation and steel or wood frame) and then the systems (plumbing, electrical, HVAC) and then the finishes, so it’s unlikely that an earthquake will hit when a project is overly structurally vulnerable. In fact, a partially completed building might perform a bit better structurally in an earthquake as the structural elements would be compelted and there would be less weight hanging from the structural frame. Also, if there is a major earthquake event during construction, the builders would have engineers check your building top to bottom to make sure it was structurally sound so they could get the building permits signed off as well. Also, I’d think you might be able to back out of a purchase contract if such an event happened (not sure about that though). Overall, a lot of other people would have a lot more to worry about than you if that happened.
Speaking about earthquakes. Is there a website where I can look at how sturdy/sound the land is before I buy in a certain area? I have always been worried about moving to the Marina or to what is now “South Beach” where the land is mainly fill and may liquefy during an earthquake.
Is there a website where I can look at how sturdy/sound the land is before I buy in a certain area?
Here is the link: http://quake.abag.ca.gov/
While both Marina and South Beach is landfill, I’d consider South Beach much more safe in an earthquake. These are new buildings, where the codes require builders to pile down to the bedrock. In the Marina, these buildings were all built before these new standards came into place and we all saw what happened to those homes that collapsed and caught on fire in the Marina in the ’89 quake.
I’d consider South Beach much more safe in an earthquake.
Agreed. I’m no seismic engineer, but I would guess that during a moderate liquefaction event the new South Beach condos will stand firm, but the land around them might slosh as it pleases taking roads and gas lines with it. So, having pilings to bedrock only buys you so much — I’d be a lot happier on higher/firmer ground. I wonder how prone South Beach is to post-quake fires relative to the Marina (as I understand it that’s a bigger issue than the earthquake itself)? Concrete and steel buildings probably don’t burn as easily, but they’re much bigger than Marina construction which I assume has more wood.
If you are at all concerned, you should without a doubt, contact someone who specializes in matters of the sort (e.g. Structural Engineer). Be careful of any “anonymous” “tipsters”.
Anon 12:42 – thanks for the ABAG link. Bad design but great info.
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http://www.rinconneighbors.com/rinpt52.jpg
Picture of original SF Shoreline in 1852 before much of what we now know as South Beach and Mission bay were created. Lots of young dirt and boats buried under all that new construction!?!?!