This book presents 8 methods for estimating seismic input, ranging from simplified and direct approaches, through the standard elastic response spectrum and artificial accelerograms, to more complete methods such as seismic hazard analysis (probabilistic, deterministic, and physically based). It also introduces general concepts of seismology and earthquakes, including seismic waves and magnitudes. Finally, 5 case studies from research and professional projects involving structures subjected to earthquakes are presented to highlight key issues in seismic design. The approach is educational, methodological, and conceptual, making the content accessible to undergraduate students interested in earthquake engineering, particularly in the context of buildings, civil works, and industrial structures. The case studies enhance the textbook's practical value and make it more engaging.