| If You Want A Big Scare. . . | July 11th, 2008 |
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The first one shows the City’s seismic hazard zones. Be patient- it took about 45-60 seconds to download. This map shows areas susceptible to slides as well as where the liquefaction zones are. The second is the USGS Earthquake Susceptibility Map for the entire Bay Area. It’s not as easy to read on a street level as the first map, but it does grade the entire bay area into 5 different zones from very high to very low danger. Deciding whether to buy in ‘earthquake country’ hinges on your attitude and how educated you are on the matter. If earthquakes scare you to death no matter what, you probably shouldn’t buy in the Bay Area- and you maybe shouldn’t live here either. If you are prepared to take the risks of living with the possibility of earthquakes, understanding what liquefaction means and how different kinds of construction respond to it will help you decide where and what you want to live in. We have an earthquake guide that we provide to all our buyers, which has a lot of good information on these topics. I have what many might call an overly laissez-faire attitude towards earthquakes. I’ve lived in the Bay Area all my life and have experienced dozens of tremors over the years, including the 1989 Loma Prieta, which I admit was a near-death experience for me. The aftermath was also frightening, especially in the Marina District, which was essentially uninhabitable for many weeks. For years after Loma Prieta, real estate north of Lombard was a very tough sell. The buildings that suffered the most damage from Loma Prieta were ’soft-story’ apartment buildings situated on corners with garages on both sides. With lots of open space and few walls on the first floor these kinds of structures were highly susceptible to collapse. Some smaller brick buildings were also severely damaged, particularly South of Market. Today, most older buildings at a minimum have bolted foundations, which help keep the structures from jumping off their foundations. Corner buildings in the Marina have also generally been reinforced to prevent collapse. And the City passed a law that required all brick buildings to be reinforced with steel beams. The City also passed stringent new building codes post Loma Prieta, which they further strengthened (no pun intended) after the 1994 Northridge quake. Brick foundations remain a concern– and some properties built before 1906 still have them. I used to see brick foundations all the time when I started selling real estate in 1986. Now they aren’t so common, as owners over time have replaced them with concrete. Others have chosen to cap the brick with concrete, which helps, but isn’t the perfect solution. My last home had a brick foundation and the house I live in now has a mixed foundation of brick, capped brick and concrete. I’m aware that this isn’t ideal and plan on eventually correcting this very expensive problem. I also live in a liquefaction zone, but choose not to lose sleep over it. This may seem naieve, but it’s an attitude I share with thousands of others, who have all decided it’s worth the risk. Leave a Reply |
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Following are two links to maps that outline geological conditions in San Francisco.