Lecture, three hours; discussion, two hours. Enforced requisites: Mathematics 31A, 31B, 32A, Physics 1A (or 1AH), 1B (or 1BH). Recommended: course 71, Mathematics 33B. Earth mantle and core. Elasticity, seismic wave equation, ray theory, travel time inversion, surface waves, free oscillations. Earthquakes and source theory. P/NP or letter grading.