- Surface geology can amplify the earthquake ground motion.
- The same districts in San Francisco that were strongly damaged in the great San Francisco earthquake of 1906 were also damaged in the 1989 Loma Prieta earthquake.
- These damage-prone districts are built on bay mud sites that can amplify ground shaking by a factor of six.
- The role of soil profiles
- Soils can be important in whether and how a house is impacted by an earthquake
- Earthquake forces travel through rock and soil under the house
- The surface soils act to either amplify or diminish the earthquake force
- Sand sites can amplify shaking by a factor of two.