This book explains the physics behind seismic ground motions and seismic waves to graduate and upper undergraduate students as well as to professionals. Both seismic ground motions and seismic waves are terms for "shaking" due to earthquakes, but it is common that shaking in the near-field of an earthquake source is called seismic ground motion and in the far-field is called seismic waves. Seismic ground motion is often described by the tensor formula based on the representation theorem, but in this book explicit formulation is emphasized beginning with Augustus Edward Hough Love (1863 - 1940). The book also explains in depth the equations and methods used for analysis and computation of shaking close to an earthquake source. In addition, it provides in detail information and knowledge related to teleseismic body waves, which are frequently used in the analysis of the source of an earthquake.