Seismic retrofitting strengthens buildings to survive earthquakes. Soft-story strengthening addresses buildings with weak lower stories. Shear walls or bracing add lateral strength. Connection upgrades ensure loads transfer properly. Foundation anchoring ensures buildings remain connected during earthquakes. Cripple wall bracing strengthens short walls between foundation and first floor. Moment connection upgrades in steel frames increase ductility. Concrete shear walls add strength without major modifications. Base isolation decouples building from ground motion. Bearing pads between building and foundation absorb earthquake energy. This system is most cost-effective for new construction. Tuned mass dampers reduce building movement. Dampers with large masses absorb energy. Pendulum dampers are used in tall buildings. Damping systems reduce occupant discomfort and building damage. Bracing systems including diagonal braces increase strength. Stiffness increases dramatically, reducing deflection. Bolted connections must be strengthened to transfer new loads. Material testing determines if existing materials are adequate.