sheila

Hello! Does anyone know where I can find information about which areas of Seattle would be most hard-hit in an earthquake? I did a search and am having trouble finding information. We're looking for a place to live and would like to take this information into account. Thank you!

John

Sheila, all of the region is prone to earthquake hazard, just like the rest of the whole west coast (part of the "ring of fire.") Regarding specific areas where more damage might occur than in others, the general rule is that areas built on landfill (for example, the Pioneer Square and SoDo neighborhoods south of downtown Seattle, some lakeshore or beachfront areas) are more hazardous because the uncompacted soil can "liquify" during seismic events, or hillsides that can slide. Most of the damage in Seattle from last February's quake was in those areas. Of course the big thing is where you are relative to the fault, or how deep or what type of quake it is, etc. There are no public-use maps showing earthquake-prone neighborhoods to my knowledge; I imagine the insurance companies would snap those up in an instant, then bad luck to folks who live there...

One thing from last year, though - it's an evolving science. New faults or active faults previously thought benign are found all the time.

You're still safer from earthquakes in Seattle than tornadoes in Oklahoma or hurricanes in Florida. For what that's worth.

Susan

Sheila, I will try to put your mind at ease, though I know some people have a real fear of these things. I've lived in California all my life, felt a good number of earthquakes, most of them just little rumbles. I also lived in southern California during the Northridge quake and in northern California during the Loma Prieta quake, both "big ones." My houses didn't sustain any damage, no one I knew was injured and no one I knew had more than a few plates broken. A very small number of people died or were injured. Some people had structural damage to their homes or businesses, but they were very much in the minority. In earthquake-prone areas the buildings and roads are all seismically designed to move with a quake and not "break." When you compare the loss of property and life in earthquakes to floods from hurricanes there is no comparison.

That said, it is better to live in a house built on bedrock as opposed to landfill. Even so, you would still probably be safer living in a house built on landfill in an earthquake-prone area than anywhere in a hurricane's path.

kam

Well said, Susan. We lived in southern CA during Northridge and sustained minor damage only but my brother in law's house was totally destroyed. So much seems to be determined by the construction of the home and the exact location viz a viz all the little fault lines. Agree about the hurricanes, but did you know we had a tornado warning yesterday in the Bay area???? Yipes. Two weeks after Northridge a tornado in Illinois killed two more people than were killed in Northridge.

BTilke

When we first moved to WA state we attended a Red Cross seminar on earthquake preparedness. They brought along with them a detailed geological map of the area that showed which were the safer and which were the more dangerous areas. You could contact the local Red Cross, ask who their earthquake expert is, and see where you could get the information for the locations you have in mind. The class, FYI, was very interesting and if they run one in Seattle, plan to attend.

tahquitz

Get a copy of the city and county general plans. They will have maps in them pertaining to geologic hazards. Fault lines are not the only consideration. Typically, it is a combination of a groundshaking, soil type and the presence or depth to groundwater that make the difference. Construction would be subject to codes, which have standards in them for structural design.

kam

One recommendation since Northridge is that all older homes be bolted to their foundations so they don't shift off it. There is also reinforcing to be done under the house in the crawl space. When you find a home you like you might want to talk with a structural engineer or earthquake retrofitting service.

ldsant

http://www.geophys.washington.edu/recenteqs/Maps/Seattle_Region.html

Here is a site that should get you started. I live in Seattle (building is on Lake Washington) and although I definitely felt the e-quake this last March, the damage that was done was aesthetic as opposed to structural (although I did have some broken crystal and plates, etc.). I'm more concerned about damage when I travel I-5 than I am about an earthquake!

ALF

John has it right. The faults in the Puget Sound region are quite deep, producing very different styles of ground motion compared to, for example, California. It would be smarter to avoid valleys and fill areas, as opposed to trying to locate fault traces. Buy a house on top of a hill, as opposed to the slopes where there may be a potential for landslides. Because most of the quakes are deep, much of the energy gets attenuated before reaching the surface, so the same magnitude quake will cause much less damage than a shallower CA-style quake. On the other hand, Seattle should expect to get a Great quake some time in the next few hundred years. This will be a deeper-seated subduction zone quake that ruptures a large surface between the North American and Juan de Fuca plates. When that happens, a catastrophic temblor will result.

sheila

Many thanks for your helpful responses! You all are great!