November 1, 2008 by Canadian Underwriter
CASCADIA EARTHQUAKE DAMAGE MIGHT BE LOWER THAN INITIALLY ASSUMED
Updated earthquake research by the United States Geological Survey is reporting that expected damage to buildings as a result of a Pacific Northwest earthquake in the Cascadia Subduction Region (which also affects B. C.) could be lower than initially assumed. The research includes the use of “Next-Generation Attenuation (NGA) Equations,” which predict how ground motion decays with increasing distance from an earthquake’s epicenter. Based on its use of NGA equations, the latest earthquake research shows a changing modelled hazard of between -15% and +5% in the Pacific Northwest region of the United States.
“Based on the shape of a building damage function for earthquakes, the amount of damage a building incurs rapidly decreases as the ground motion decreases (all other components remaining unchanged),” the report notes. “Therefore, a 20% increase in hazard can equal a 30-50% decrease in expected damage.”
These observations could have a bearing on earthquake modelling done by AIR, EQECAT and RMS, Willis notes.
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