Principles of elasticity, stress and strain, seismic waves, rays and wave-fronts, Fermat principle, Huygens principle, Snell’s law, study of the Earth from seismic waves. Principles of seismic reflection, principles of seismic data processing and interpretation. The gravitational field of the Earth, use of gravimetric methods to study the subsurface. The magnetic field of the Earth, the use of magnetic methods to study the subsurface.