LIVING WITH EARTHQUAKES IN THE SF BAY AREA

David O.Y. Wong

The San Francisco Bay Area (SFBA) where we live, work and play appears very nice environmentally and climatically with abundant sunshine, open space, trees and hills surrounding us, but not so geologically. The area is still very active in terms of earthquakes and many unstable slopes vulnerable to landslips. Statistics may bother or frighten you, or you may not believe it, but SFBA has on average some 25-40 minor earthquakes (at magnitude 3 or below) every week, most of which are hardly noticeable. Of course we did have some more powerful and destructive quakes from time to time with substantial ground shaking followed by numerous after-shocks, such as the episodes in 1860-70, 1906, 1989 and more recently in 2008 near Milpitas.

When the earth moves or shakes violently, many horrific disasters leading to extensive fatalities, injuries, property losses and service disruption can happen, such as house/building destruction or sinking, leakage or breaking of water and gas pipes and power lines causing fires, electricity and water outages for days.

Most earthquakes occur along or near fault lines or zones which are remnants of interfaces and tectonic movements between the major continental “plates” (land masses including those beneath oceans). These “plates” were once joined together millions of years ago and subsequently detached via huge earth forces to form the existing continents, islands and oceans of our planet; and the fault lines have since been active as manifested by volcanic and other eruptions (vertical movements) and lateral tensions (horizontal movements). The latter is evidenced by the shifting or slippage/disjointing of roads, railway and power lines, bridges and fences. When large tensions occur, energy from within the earth’s crust is released and radiated outward from the epicenter as in the 1906 quake which affected over 350 miles along the San Andreas fault and destroying a large portion of San Francisco via shaking, land/building subsidence especially on loose soil (a process called “liquefaction”), and explosive fires mainly from gas and oil leaks and power-line breaks. Large shakes or volcanic eruptions under oceans or along coastal areas may also produce huge tsunamis which can roll over thousands of miles of sea to the other sides of the ocean as seen in the magnitude 8.9 quake in Indonesia in 2004 and similarly in Japan in 2011 .

Our California coastal region forms part of an extensive “Pacific Ring” edging around the Pacific Ocean from South and North America to East and Southeast Asia and Oceania/New Zealand with many active volcanoes, fault lines and hence earthquakes. We have three major fault lines among many others in SFBA – the notable San Andreas, Hayward and Calaveras faults (see map). And so, our land is far from being stable geologically and seismically! The epicenters of the 1906 and 1989 quakes were both located near San Andreas fault (west of SF and Loma Prieta respectively). Many forecasts have indicated that there is a 62% chance that the Bay Area might again be hit by a magnitude 6.7 or higher earthquake before 2032.

The 1906 and 1989 quakes are well documented and widely exhibited, and we are time and again being reminded by government and other agencies including the US Geological Survey (USGS), states and counties/cities to take adequate precautionary measures to reduce or minimize the impacts of major quakes in future. We must all increase our disaster preparedness while living in the Bay Area. The following, among others, are worthy of our attention and action:

  • When looking for a house, condo or apartment to move to, try to avoid those located on sandy or clay soils including landfill areas along low-lying coastal areas susceptible to flooding and liquefaction (e.g. in SF’s Marina District during the 1989 quake). Higher grounds or sites on hard rocks are better localities for homes.
  • For older houses built before 1991-93, arrange for relevant seismic inspection and retrofitting works including garages, windows and roofs to make them safer from major quakes, and also replace aging or rusty water and gas pipes where needed via qualified contractors.
  • A safe home is a happy home. Do not hang heavy, glass or fragile objects like large picture frames above beds and sofas, and secure loose and tall materials including bookshelves and cupboards to reduce the damages and injuries from falling or shattering objects caused by intense shaking. Take good care of children.
  • Familiarize with your neighborhood environment and know your neighbors, helping each other when necessary during disasters. Liaise with and know the location of your nearest Police and Fire Departments and clinic/hospital for emergencies and to learn whether there is a Community Emergency Response Team (CERT) in your area. Also identify a few relatives/friends (who should have your vital information) living outside SFBA so that they can contact you or the Police in case of disasters.
  • Identify a safer spot both inside and outside your home to hide or escape during a major quake, such as any nearby open space/park, school and community center. If inside homes, hide underneath wooden, not glass tables or benches.
  • Park one of your cars outside your garage where practicable (e.g. on your driveway or curbside) to provide for an additional escape means after a major quake which may damage the garage door making it unable to open even by hand.
  • In preparing for possibly a few days or more without any tap water, electricity, gas supplies and house phone after a major quake, assemble a “survival kit” including but not limited to around 3 days’ supply of drinking and consuming water (about 1-2 gallons per person per day), bread and canned foods, portable cooking device, utensils, transistor radio and torches (battery or solar powered), first-aid kit, packed clothing and shoes, and other items. Be mindful of the expiry dates of foods. The bottled water should be changed every 6 months.
  • Also attach a few warm clothes, a pair of walking shoes and your handbag with cash, important information (driver license/ID card, SSI and passport/Green Card numbers, credit cards, AAA member card, etc.), daily medication (if any), candies/high-nutrition snack bars and bottled water by your bed-side in case you have to vacate your home during a major quake or fire in the middle of the night when you won’t have any time to pack up!
  • Consider buying earthquake insurance (different from and not covered by homeowners’ and other insurances) especially for homes more vulnerable to quakes.
  • Keep separate copies of your important records outside your home, including passport/Green Card, driver licenses, mortgage/lease or rent agreements, bank and credit card statements, etc.
  • Although large-scale tsunamis from Pacific Ocean are infrequent in SFBA, residents in low-lying coasts (e.g. Sunset District in SF, Pacifica, Half Moon Bay) should still be vigilant and take the necessary precautionary measures.

In general, get prepared for major disasters before they strike us!