Presenting a comprehensive introduction to the propagation of high-frequency body-waves in elastodynamics this volume develops the theory of seismic wave propagation in acoustic elastic and anisotropic media to allow seismic waves to be modelled in complex realistic three-dimensional Earth models. The book is a text for graduate courses in theoretical seismology and a reference for all academic and industrial seismologists using numerical modelling methods. Exercises and suggestions for further reading are included in each chapter.