Amplification: A Secondary Earthquake Hazard
Amplification is the increase in the shaking of the ground during an earthquake due to factors such as earthquake magnitude, distance from the epicenter, and local geological conditions. Ground shaking increases as earthquake magnitude increases and distance from the epicenter decreases. The other factor, local geological conditions, is less straightforward.
What Are the Threats?
Generally, loose sediments shake significantly more than dense bedrock. Therefore, certain areas along the Pacific Northwest coast, such as river valleys and floodplains, are more susceptible to amplification. An increase in amplification is also associated with an increase in liquefaction potential. Flat areas with loose sediments and rich soils are prime locations for human development, but these areas are also prone to amplification hazards. Therefore, proper zoning and building standards should be enforced in these hazard areas.