Rotation is caused when the outer side of the foundation is saturated with moisture while the soil in the crawl space is dry.  When the house was built, its weight pressed evenly on the inside and outside of the foundation. When the soil on the outside becomes soft and saturated the foundation starts to sink on the outside edge.  This causes the outside edge of the foundation sink into the ground and the inside edge pull up. This has ZERO impact on a foundation’s ability to hold a house up off the ground or its ability to perform in an earthquake so long as you attach the house to it with a retrofit.