The Applied Technology Council (ATC) is pleased to report on the completion of the 3rd ATC-35/USGS Workshop on National Earthquake Ground-Motion Mapping on Thursday and Friday, December 7-8, 2006, at the Marriott Hotel in San Mateo, California.  The Workshop was convened by ATC and the U.S. Geological Survey (USGS) and a number of co-sponsoring organizations.  Like the first and second ATC-35/USGS Workshops on National Earthquake Ground Motion Mapping, which were held in 1995 and 2001, respectively, this Workshop provided input from the structural engineering, geotechnical engineering, geosciences, and risk modeling professions to the USGS on key issues that affect the preparation and use of the next round of national earthquake ground motion maps (and related products).  The Workshop also provided input to organizations responsible for the selection and adoption of ground motion maps in model seismic regulations and actual seismic codes governing the design of buildings, bridges, and other structures. In addition, the Workshop discussed potential new map-related products.

Following is a list of topics addressed at the Workshop:

A.     Issues for Preparation of USGS Probabilistic National Ground Motion Maps

• Which ground motion attenuation relationships should be used for national ground motion mapping?
• Should the reference geologic condition used for national ground motion mapping be changed?
• Should near-source directivity effects be incorporated in national ground motion mapping?
• Should time-dependent probabilities be incorporated in national ground motion mapping?

B.     Issues for Selection and Modification of Ground Motion Maps for Use in Design of Buildings, Bridges, and Other Structures

• Which return periods should be selected for design and how should they be determined?
• Should the probabilistic maps be bounded by deterministic ground motions and how should the bounds be quantified?
• How should design response spectra be developed using the design ground motion maps?

C.     Map Products and New Directions

• What paper maps and electronic products should be provided for users of national ground motion mapping (e.g. ground motion values, de-aggregation maps, acceleration time histories)?

Click Here for More Information, Including the Complete Workshop Program and Location Map

Post-Workshop Corrections and Additions (as PDF files):

Part II-A: Which Return Periods Should be Selected for Design and How Should They be Determined?.

• Speaker 17: James Harris Presentation and Abstract, updated 1/2/2007

Persons requiring additional information on the Workshop should contact the Applied Technology Council, 201 Redwood Shores Parkway, Redwood City, California 94065; Phone, 650/595-1542; Fax, 650/593-2320; e-mail, ATC@ATCouncil.org.