Your foundation may be in need of repair to make a seismic retrofit possible, cracks must be filled with a high strength epoxy and then steel straps are bolted across. 

In extreme situations a foundation may be in need of replacing, this can be done safely with an experienced crew of technicians.  An entire new foundation can be poured and the house bolted per new construction standards to prevent future damage 

Piers and Posts are responsible for supporting your home  When these become undermind due most commonly water that has seeped through the cracks. Your home may become out of level, causing doors and windows to become misaligned, cracks or tears in the dry wall.