Seismic code limit states design philosophy. In February 2004 a new set of seismic codes was issued. In Spain the seismic code is called the "Norma de Construcción Sismorresistente". (See the ) In the United States the Federal Emergency Management Agency (FEMA) publishes "Recommended Seismic Provisions for New Buildings and Other Structures". Seismic code Seismic codes or earthquake codes are building codes designed to protect property and life in buildings in case of earthquakes. The need for such codes is reflected in the saying, "Earthquakes don't kill people—buildings do." Or in expanded version, “Earthquakes do not injure or kill people. Poorly built
Seismic tomography better understand core, mantle, and plate tectonic processes. Tomography is solved as an inverse problem. Seismic travel time data are compared to an initial Earth model and the model is modified until the best possible fit between the model predictions and observed data is found. Seismic waves would travel in straight lines if Earth was of uniform composition, but the compositional layering, tectonic structure, and thermal variations reflect and refract seismic waves. The location and magnitude of these variations can be calculated by the inversion process, although solutions to tomographic inversions are non-unique. Seismic tomography is similar to medical x-ray