Structural Engineering is the practice of designing and evaluating buildings and structures for their ability to support loads from their own weight and the things they contain (sometimes called gravity loads) and to withstand the forces of nature like wind, snow, and earthquakes (sometimes called environmental loads and lateral loads).
In California, Structural Engineers are required to have additional knowledge of the design and evaluation of structures to withstand large earthquakes. This typically requires an evaluation and strengthening of the building’s ability to withstand lateral or side-to-side motion.