Reinsurance (November 01, 2008)

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.