Catastrophe risk modeling firm AIR Worldwide Corp. (AIR, Boston) announced the availability of an update to its probabilistic earthquake risk model for the United States, which is used by insurers, reinsurers, corporations and government agencies to assess and manage earthquake risk. Highlights of the enhanced model include: an updated view of seismic hazard in the U.S. that is consistent with the 2008 U.S. Geological Survey (USGS) National Seismic Hazard Maps; an updated approach to estimating earthquake-induced ground motion based on the Next Generation of Ground-Motion Attenuation Models (NGA) project; and updated damage functions based on analysis of damage and claims data and three-dimensional engineering analyses performed by AIR engineers and other researchers. The updated AIR Earthquake Model for the U.S. is available in Version 11.0 of AIR's CLASIC/2, CATRADER and CATStation catastrophe risk modeling applications.
The USGS recently updated the National Seismic Hazard Maps by incorporating new seismic, geologic, and geodetic information on earthquake rates and associated ground shaking. Producing the update involved interactions with hundreds of scientists and engineers, including AIR researchers, at regional and topical workshops, according to AIR. The AIR model is consistent with the USGS update, which represents the best available science on U.S. earthquake hazard, the company says.
The NGA equations are used for predicting ground motion generated by earthquakes. They were the result of a five-year multidisciplinary research program coordinated by the Pacific Earthquake Engineering Research Center (PEER) in partnership with the USGS and the Southern California Earthquake Center (SCEC). The resulting NGA equations incorporate significantly more ground motion data and data of better quality, particularly at close proximities to high-magnitude earthquakes, and provide a more robust method for estimating ground motion, says AIR. The damage functions in the model were updated based on engineering analysis, a thorough understanding of building codes, the results of published studies, and analysis of detailed claims and damage data. The breadth and depth of recent USGS changes prompted AIR engineers to reexamine existing claims and damage data, not only with respect to the 1994 Northridge, Calif., earthquake, but also for more recent events such as Nisqually (2001) and San Simeon (2003). This reexamination has led to an even deeper understanding of vulnerabilities of structures to earthquakes, AIR reports.
The enhanced methodology used in the development of AIR's damage functions is the same as that recently adopted by major research universities, the Applied Technology Council, FEMA and PEER. Certain applications of the methodology used by AIR engineers have been funded by the USGS. The damage functions of the model have been peer reviewed by Stanford University Professor Greg Deierlein, Director of the John A. Blume Earthquake Engineering Center and Deputy Director for Research of the Pacific Earthquake Engineering Research Center, and Dr. Charles Kircher, Principal at Charles Kircher & Associates and a key developer of HAZUS.