Applied Technology Council A Nonprofit Corporation Advancing Engineering Applications for Hazard Mitigation California - Washington, DC Area

NEWS RELEASE November 12, 1999

For More Information, Contact: A. Gerald Brady, 650/595-1542 E-mail: atc@atcouncil.org

ATC Publishes ATC Techbrief 2, Earthquake Aftershocks -- Entering Damaged Buildings

The Applied Technology Council (ATC) is pleased to announce the immediate availability of ATC TechBrief 2, Earthquake Aftershocks-Entering Damaged Buildings. This is the second in a series of TechBriefs prepared by ATC to synthesize and summarize important research information for use by practicing structural and geotechnical engineers.

ATC TechBrief 2 offers guidelines on the length of time to wait before entering earthquake-damaged, but stable, buildings under emergency conditions. The guidelines are based on aftershock research by scientists at the U.S. Geological Survey and are linked to the ATC-20 postearthquake building safety evaluation procedures. The ATC-20 procedures are widely used by building departments and volunteer structural engineers to identify and post buildings as INSPECTED (green placard), RESTRICTED USE (yellow placard), or UNSAFE (red placard).

Information and guidance are provided on:

• how to classify a damaged building as unstable;
• the number of days to wait before emergency entry of buildings posted as UNSAFE, but stable (the waiting period is a function of mainshock magnitude, duration of time to be spent in the building, and assumed level of acceptable risk);
• aftershock activity, including aftershock sequence patterns and stress distribution, the size of aftershock hazard areas, the relationship between aftershock magnitude and damaging ground motion, and the probability of aftershocks;
• applicability of the recommendations to search and rescue operations; and
• cautionary warnings.

ATC has printed 10,000 copies of ATC TechBrief 2 and will be distributing them on a complimentary basis to ATC subscribers and to members of professional associations concerned with postearthquake building safety evaluation-California Building Officials, the Structural Engineers Association of California, and structural engineers associations in other seismically active states.

ATC TechBrief 2 is one of several TechBriefs being prepared under the ATC-35 project, "Enhancing the Transfer of U.S. Geological Survey Research Results into Engineering Practice." ATC TechBrief 1, Liquefaction Maps, which was released by ATC in March 1997, inventories and describes the available regional liquefaction hazard maps in the United States.

Other TechBriefs are planned, and topics are expected to include both geotechnical and structural engineering issues. All TechBriefs will be available on ATC's world wide web site: www.atcouncil.org. Copies (one per customer) can be ordered from Applied Technology Council, 555 Twin Dolphin Drive, Suite 550, Redwood City, California 94065 (Phone, 650/595-1542; Fax, 650/593-2320; E-mail, atc@atcouncil.org).

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