The Golden Gate Bridge

March 10, 2006

STRUCTURAL ENGINEERS SAY SF BAY AREA IS BETTER PREPARED THAN EVER, BUT MANY COMMUNITIES ARE STILL NOT COMPLETELY READY FOR NEXT QUAKE

“Earthquakes may be inevitable, but the degree of damage they may cause is NOT inevitable.”

SAN FRANCISCO, MARCH 10, 2006 – The Structural Engineers Association of Northern California (SEAONC) believes that the Bay Area is better prepared than ever to withstand a major earthquake but that many specific communities are not as prepared as they should be. The predicted loss of life and the anticipated economic disruption, the group says, should be considered unacceptable.

SEAONC reports that people will be relatively safe when the next major earthquake occurs if they are in buildings built after the mid-1970’s or in older commercial and residential establishments that have already undergone a seismic retrofit. However, buildings and infrastructure built before the 1970’s that have not been strengthened may suffer major damage or completely collapse.

“The expected losses of lives, homes and livelihoods, similar to the devastation in the Gulf Coast following Hurricane Katrina, will be caused not only by acts of God, but also by the failures of many individuals in the private and public sectors who have not yet taken necessary action to minimize potential disruption,” said Patrick Buscovich, a prominent Structural Engineer who is part of the SEAONC ’06 Centennial Planning Committee and one of its past presidents.

Buscovich also serves as a board member of Applied Technology Council of Redwood City, an engineering research group that conducted a yearlong study for the City of San Francisco in 2003 entitled “San Francisco's Earthquake Risk.”

There are many facts as well as helpful information that decision makers and the public continue to under-value, SEAONC believes. (For more detailed information about these facts, please see the attached Backgrounder or visit http://www.celebratingeqsafety.com/) These fall into three categories:

  • Scientific predictions (“It won’t happen during my lifetime,” “I survived 1989 so my house/business will surely survive the next big one,” “I can’t do anything about it.”)


  • Studies of how the built environment will respond to the next major quake and which neighborhoods and types of structures are at biggest risk.


  • Available information and action plans to protect one’s home, office, property – and lives.


Regarding the studies of how the built environment will respond, Buscovich cited the following predictions from the report, “San Francisco's Earthquake Risk,” in the event of a magnitude 7.2 earthquake along the San Andreas Fault:

-- 29,862 buildings citywide would be destroyed by the shaking and post-earthquake fire.


-- 20,857, or 70 percent, of those structures would be in the residential Richmond, Sunset, Twin Peaks, Ingleside and Excelsior neighborhoods.


-- Tens of thousands of residents will be made homeless by the destruction of nearly 30,000 houses and apartments -- or about 9 percent of the city's housing stock.


--Depending on the time of day, the report predicts between 366 to 651 people would be gravely hurt or killed instantly with thousands more sustaining minor to serious injuries.


--Of the estimated $13.7 billion worth of destruction, about half would befall residential structures, according to the report.


--The housing stock is said to be particularly vulnerable because of the prevalence of "soft-story building" structures, that contain stories that are substantially weaker and more flexible in a horizontal direction, usually due to garage or extensive window openings at street level.


-- There may be as many as 5,000 “soft-story” buildings in the City, each one housing many families. Particularly at risk are corner buildings with retail establishments on two sides or streets. These retail/commercial stores usually have few interior partitions or shear walls and many large windows. These conditions weaken the structure's ability to withstand earthquake motion.


-- The total economic losses from housing alone would reach $13.7 billion citywide, (based on an average assessed value of $100/per square foot, not the average market value believed to be $200/per square feet).


“Earthquakes may be inevitable, but the degree of damage they may cause is NOT inevitable,” said Buscovich. He noted that SEAONC and other engineering organizations continue to study and research soils, structures and earthquakes and their interrelationship. This information is then shared within the structural engineering community, with other professionals such as architects, builders and developers, and with government officials, individuals and business owners who are interested in minimizing losses during an earthquake.
Founded in 1930, the Structural Engineers Association of Northern California (SEAONC) is committed to the advancement and incorporation of the state of the art in structural engineering standards and practices through applied research, continuing education, and the promotion of professional relations among Civil, Structural, and Geotechnical Engineers.

Contact: Patricia Coate 415-309-2231

PR Contact for Structural Engineers Association of Northern California

Cell: 415-309-2231
Fax: 415-449-6555
1933 Webster Street
San Francisco, CA 94115




BACKGROUNDER

#1: Ignoring Scientific Predictions – and the excellent work of geoscientists over past 100 years

Scientists know why earthquakes occur here—The Bay Area straddles the boundary where two of the Earth’s largest tectonic plates meet and slowly move past one another. When boundary faults break and the North American and Pacific Plates lurch past each other, quakes occur.

Scientists know large and damaging earthquakes are certain to occur in the future—At least eight faults in the Bay Area are capable of producing earthquakes of magnitude 6.7 or larger. Such quakes can kill and injure many people and cause substantial damage to buildings, roads, bridges, and utilities. (http://pubs.usgs.gov/gip/2005/15/)

Scientists know that there is a 62% probability that at least one earthquake of magnitude 6.7 or greater will occur on a known or unknown San Francisco Bay region fault before 2032. After a century of study by geologists, many faults have been mapped in the region, but not all faults are apparent at the surface—some quakes occur on previously unknown faults.

Scientists and engineers have studied the 1906 quake and now understand that the largest shaking during that earthquake occurred in areas (such as the Sunset and Richmond districts) where few people lived at the time. The next eruption of the San Adreas fault will likely be further north than in 1906 and nearer these districts. Scientists believe that shaking in these heavily populated areas could be six times stronger than downtown SF in 1906.

#2: Ignoring Studies – and Predictions -- of Potential Effects on our Built Environment

Here are the predictions of the structural engineers research group, Applied Technology Council of Redwood City, outlined in “San Francisco's Earthquake Risk," a yearlong study commissioned in 2003 by the City of San Francisco. The group predicted that in a magnitude 7.2 earthquake along the San Andreas Fault:

-- 29,862 buildings citywide would be destroyed by the shaking and post-earthquake fire.


-- 20,857, or 70 percent, of those structures would be in the residential Richmond, Sunset, Twin Peaks, Ingleside and Excelsior neighborhoods.


-- Tens of thousands of residents will be made homeless by the destruction of nearly 30,000 houses and apartments -- or about 9 percent of the city's housing stock.


--Depending on the time of day, the report predicts between 366 to 651 people would be gravely hurt or killed instantly with thousands more sustaining minor to serious injuries.


--Of the estimated $13.7 billion worth of destruction, about half would befall residential structures, according to the report.


--The housing stock is said to be particularly vulnerable because of the prevalence of "soft-story buildings," structures that contain stories that are substantially weaker and more flexible in a horizontal direction, usually due to garage or extensive window openings at street level.


-- There may be as many as 5,000 “soft-story” buildings in the City, each one housing many families. The risk is due to the garage door openings and the extent of window openings at street level. Particularly at risk are corner buildings with retail establishments on two sides or streets. These retail/commercial stores usually have few interior partitions or shear walls but many large windows. These conditions weaken the structure's ability to withstand earthquake motion. (http://www.celebratingeqsafety.com/different-structures-challenges.html)


-- The total economic losses from housing alone would reach $13.7 billion citywide, (based on an average assessed value of $100/per square foot, not the average market value believed to be $200/per square feet) with $4.6 billion, or 34 percent, sustained in the neighborhoods and low-rise commercial strips of the Richmond, Sunset, Twin Peaks, Ingleside and Excelsior.



Specific areas of the City that are on poor soils (sand, landfill, etc.) will be most affected.
  • This includes portions of Mission Bay, the Embarcadero, SOMA, the Civic Center and Marina Districts. In these areas we can expect general extensive damage to most buildings, with a number of collapses, particularly of older buildings. Expect extensive liquefaction, settlement, and lateral spreading of surface soils, with large ground fissures and settlement, extensive disruption and failure of underground water, sewer and gas lines.


  • In the Avenues, many homes, especially those built over garages, will be extensively damaged and a significant percentage, particularly buildings on corners may collapse. This will be similar to what happened in the Marina District in 1989 but more extensive throughout the City.


  • In the financial district, Structural Engineers expect most buildings, including new ones, would have some damage. Many will be able to be occupied after a few days of clean up, but will likely be subjected to continuing construction activity for weeks to months. A number of buildings particularly older ones may be closed during repair, which could take many months to years.


  • In the Russian Hill, Cathedral Hill and Pacific Heights regions, tall multi-family residential buildings, will likely be severely damaged and a few of these buildings may collapse.


  • The potential for conflagration, as occurred in 1906, is still very real.


#3: Not Acting on Available Information

There have been many pamphlets and articles written about what individuals can do to cost-effectively secure a single-family residence or a more complex structure against the dangers of an earthquake. Yet, the public and business owners alike are often too complacent. That’s why the Structural Engineers have started a campaign to raise the awareness of the public on what individuals need to know and can easily do. (See our website at http://www.celebratingeqsafety.com/).

It’s impossible for the homeowner to do anything bad, as long as they just do something to bolt their foundation, secure their water heater and complete other essential activities! This is the consensus of Structural Engineers who remind homeowners that most weekend home-repair buffs can do the work. Plus, there are several available resources and information online for how to do these important tasks. Need bigger work? Call in a Structural Engineer, but do these easy steps first:

  • Bolt Your Foundation

The number of foundation bolts, linear feet of plywood, and floor-to-wall connections (brackets) that are required to seismically retrofit your home varies depending on its size and weight. Remember, earthquakes will find the weak spots in your house. So, if you add bolts but not plywood, you may still have a problem when the ground shakes.

  • Strengthening your Crawl Space

Some houses have an additional area of deficiency in the foundation called an un-braced "cripple wall." This is the short wall that connects the foundation to the floor of the house and encloses the home's crawl space. These walls need to be braced with plywood. Otherwise, they have the potential to "tip" over, and cause the house to collapse onto the foundation. Install plywood on the inside surface of the crawl space extending from the sill plate to the base of the floor joist above to prevent the wall studs from collapsing.

  • Brace your Water Heater

One of the most common problems on the interior is an un-braced water heater, masonry chimneys, tall shelves and tall file cabinets. Not only can these elements cause damage to the property, any toppling could also cause severe injury. Unsecured water heaters may fall over, rupturing rigid water and gas connections. Water heaters are required to be anchored to wall studs or masonry with metal straps and lag screws. Kits are available at hardware stores and home centers. 
 If not already done, have a plumber install flexible (corrugated) copper water connectors.

  • Add Seismic Gas Shutoff Valves

Seismically actuated gas shutoff valves offer protection in the event of an earthquake by blocking the flow of gas. Commonly referred to as seismic valves or earthquake valves, these valves contain sensing mechanisms which cause the valve to positively shutoff the flow of gas upon detecting a given peak acceleration over a period of time.

  • Check your Water and Gas Pipes

Water or gas pipes anywhere in your home can break. Water leaks can cause extensive damage, and gas leaks are a major fire hazard. Have a plumber evaluate, replace, and properly secure rusted or worn water and gas pipes. 
 If not already done, have a plumber replace rigid gas connections to water heaters, stoves, dryers, and other gas appliances with flexible (corrugated) stainless-steel gas connectors (see below). 
Excess-flow gas-shutoff valves for individual appliances, which stop gas flow in case of a catastrophic leak, are also now available for use with flexible connectors. The latest recommendations of Structural Engineers, contractors, and city building officials who are experts on retrofitting are also available on the ABAG web site at http://quake.abag.ca.gov/fixit/.

Many building owners have not acted comprehensively enough to restore business operations quickly after a major earthquake. While most companies operate in buildings designed to meet the minimum level of life safety protection provided by our building codes, many have not taken the necessary, additional measures to ensure their facilities, equipment, research and manufacturing processes and other intellectual property will not be damaged during a major earthquake.

  • People will be relatively safe in buildings built after the mid-1970’s. Buildings and infrastructure built before the 1970’s that have not been strengthened will suffer major damage or complete collapse, causing thousands of casualties and extreme economic hardship.


  • There are a significant number of buildings in the Bay Area (as many as 500 in San Francisco alone) that are non-ductile concrete moment frame buildings and have not been seismically upgraded to withstand a major earthquake.


  • Unreinforced masonry buildings still pose a serious life-safety concern. Unreinforced masonry buildings are expected to account for close to 13,000 of the almost 156,000 uninhabitable units resulting from a magnitude 7.1 Hayward fault earthquake. These units house a disproportionate share of the poor, particularly in San Francisco.