How do seismic design principles inform the structural engineering of buildings and bridges in earthquake$-$prone regions? Discuss the seismic hazard assessment methods, ground motion modeling techniques, and building code provisions used to evaluate earthquake risks and establish design criteria for seismic$-$resistant structures. How do engineers incorporate seismic resistance features, such as base isolation, damping systems, and ductile detailing, into building and bridge designs to enhance their ability to withstand ground shaking, lateral forces, and structural deformation during earthquakes?