The book is dedicated to the key issues in reducing the seismic risk of structural systems. Considering the seismic activity of the region in which Bulgaria is located, the topic is extremely relevant and significant. The book reflects all the main stages of designing structures for seismic impacts. A mathematical formulation of the theoretical foundations of seismic engineering is given, with the emphasis placed on the physical essence of the problem under consideration. All theoretical statements are richly illustrated with examples, which makes the book understandable for specialists with different levels of qualification and significantly contributes to its applied focus. The presented monograph is a response to a long-overdue need for a course in seismic engineering. The potential readers of the book will be the technical and scientific community, specialists and designers, and students.