(a) A spherical and three spheroidal magma chamber models in a 3-D domain with annotated boundary conditions and dimensions. A mesh is presented for the magma chamber interface. (b) Snapshots of the ground-motion velocities in the crust and horizontal dynamic stress changes (σxx) in the spherical magma chamber with a VP/VS ratio of 1.85 at lapse times of 0.8, 1.3 and 2.0 s. (c) Peak horizontal dynamic stress changes (σxx,max) and peak dynamic pressure changes (pmax) in the spherical magma chamber with a VP/VS ratio of 1.85 and density of 2500 kg/m3 as a function of time. (d) Peak horizontal dynamic stress changes and pressure changes as a function of the VP/VS ratio in spherical magma chambers with three different densities. The peak horizontal dynamic stress changes are found to be nearly constant, while the peak pressure changes increased with the VP/VS ratio.