Fig 9. The shallow magma chamber of a volcano (krafla, in Iceland) imaged by seismic undershooting (waves undershooting the volcano from the north). (Top) S wave record section. Note shear wave shadow. (Middle) P wave record section. Note delay of P wave as it crosses the magma chamber. (Bottom) Finite-difference synthetic that matches the P wave data, computed for a 1 km thick magma chamber. From Brandsdottir et al. [1997]. (PostScript version).