Real estate decisions and ABAG quake maps (San Francisco, Oakland: for sale, rent)

[blackhaz]

Hi All,

I apologize if I am probably bringing up a topic too sensitive. I'm cultivating long term plans to relocate to Bay Area from Europe some day. I have a family with a small kid, and one of my ultimate concerns is the earthquake safety. My question is - when you settle down there, do you consider shakemaps from ABAG or USGS when you buy or rent your home?

How big of a bonus is it for you to live in a place that goes to Mercalli VII-VIII at maximum when all hell breaks loose? I'm talking scary scenarios like the repeat of the 1906 event, or both North and South sections of Hayward fault going off at the same time.

I understand those maps are all theoretical and are based on guessed magnitudes, however it makes perfect sense to me to live on a hard soil, away from the fault lines. I've identified a few "safe" pockets like Potrero Hill, south end of Noe Valley past the Clipper St, Glen Park, parts of Bernal Heights in the city, so I'm mostly targeting these areas. At the other hand, we'd probably prefer to live in Berkeley as it's less expensive and, we believe, could be less stressful, however the ABAG map goes totally dark red/black everywhere there in case of the N+S Hayward quake. (I don't remember the probability percentage but it was something real.)

Am I too paranoid? Am I thinking in the wrong direction here? I am trying to think of a few reasons one might ignore those maps. First, those maps may tell very little because the real earthquake fault may have a different "direction" to the one simulated. It was shown very well in one of the USGS papers where the same scenario resulted in a completely different level of destruction at the same location, depending on the direction of the fault. The second reason to ignore the map would probably be that wood frame houses that are properly retrofitted will survive a major event. I was not able to find what's the max Mercalli intensity a retrofitted house will survive though.. Will it survive Mercalli X shaking, or even XI?

What's your strategy?

[Isebiel]

I don't think it's too paranoid, especially if you're thinking of buying. My husband and I definitely considered shake maps when we chose where to live, eliminating the Marina, most of SOMA, and most of North Beach. It also eliminated, like you saw, pretty much all of the convenient locations in the East Bay.

After a lot of research, my impression is that a major earthquake will be really unpleasant and inconvenient for a few days -- there will be no drinking water, and many structures will require major repair. However, it's unlikely that lots of stuff will simply collapse and crush people. My strategy, after avoiding places that will have liquefaction issues, is to have enough supplies on hand to survive on my own for a few days.

Honestly, it's a minor worry after the constant threat that weather in the midwest was.

[Ruth4Truth]

Those of us who grew up there don't worry about it. There are little quakes from time to time, not a big deal, you get used to it. Better to have a lot of little quakes than one big one.

One thing that people generally don't know is that there were TWO epicenters of the 1906 quake; San Francisco and Santa Rosa. Really, there's no place to run, no place to hide; the whole place is quake-prone, so you may as well not worry about it.

[California Vagabond]

The best link I've found for this data so far is: Earthquake Shaking Maps and Information « ABAG Earthquake and Hazards Program

but blackhaz, it sounds like you might be way ahead of me on this kind of research. I had to look up the word 'Mercalli' after reading your post.

I studied the liquefaction maps and proximity to fault lines before I decided where to move, and ruled out a home in areas with high liquefaction susceptibility. I was here for the Loma Prieta quake, and well remember how badly homes in the Marina and other high liquefaction areas were hit. I shared your concerns about Berkeley.

[tanglenet]

I used the maps prior to making our purchase. Some people care about these things and some don't.

[Ruth4Truth]

People who could afford to had their houses seismically retro-fitted after the Oakland quake in the late 80's. I don't know if this was actually required by any municipalities, but if you're house-hunting, you could ask if the home was seismically retro-fitted, and if you're told it was, you can ask to see the reinforcement work done on the building's substructure to verify that claim.

[NorCal44]

We bought and consulted those maps. We are very very near to the San Andreas fault, but it was the right price and proximity to jobs. So we just avoided the homes for sale that seemed directly ON the fault line itself. I don't know how it works, but beyond the violent shaking, I would not want half of my house pulled in one direction and the other half in the opposite!

[fizbin]

Note that in the 1989 Loma Prieta quake most of the damage was 60 miles away from the epicenter. Also most of the damage was from defective building design (true of the shopping area in Santa Cruz, homes in the Marina, the bridge and the collapsed freeway). On the other hand 1989 was not the 'Big One'. As an area native I do not spend much time or energy worrying about them: secure your home, have a week of supplies around and then enjoy life and/or worry about other things.

[Joe Doggs]

When we bought back in the 80's we actually never paid any attention to EQ risk insomuch as it was a foreign concept to us. As luck would have it we ended up locating on bedrock so '89 was minimal to us. If you want to be carefull avoid landfill like the Marina or Soma or unreinforced masonry buildings. EQ engineering is a somewhat imprecise science because designers have to try and forecast the effects and then learn when a real one occurs. Statistically you are in more danger commuting than being hurt in a EQ. What makes them so scary for most is the suddenness but if you plan beforehand then worries are minimized and panic can be bad. If you do as some others have suggested then you will be ok. What I have observed is having a plan in place and worked out goes along way. Look for things like who will go for the kids and how you will communicate if you are apart. Having a out of state contact to relay messages to is good because phone traffic will be routed outward during the emergency. Fire will be the most immediate danger post quake and drinking water will be worth its weight in gold. Cruise Youtube for more specific preps then go about your life and enjoy the ride.

[kgbnsf]

If it makes you feel more comfortable, go for it. I personally didn't let it factor in my decision on where I've lived, rented and owned. I've been here 20 years with no major earthquake. It could be another 20 years before one occurs, or happen tomorrow. Looking at the last major quake, how many homes had damage? Very few. 60 something people perished out of 6 million. The odds are strongly in your favor.