I have read that both bolting and bracing of a house are recommended. What is bracing?
Many houses have a short wood framed wall, referred to as a “cripple wall”, running from the foundation to the main floor. This wall needs to be strengthened to avoid seismic collapse. With this collapse, the house appears to have been vaulted to one side on its sub-area walls. Improvement in the stiffness of these walls is needed in order to transfer the earthquake movements from the ground through the cripple walls to the house. This forces the foundation and the house to move together. Differential movement is reduced by turning some of the sub-area walls into “shear walls”, which consists of attaching structural plywood to the walls to create the desired strengthening or stiffness.