Strange Seismic Waves

Zurich geophysicists are now capable of modeling the dynamics behind crustal plates and indicate the variations of materials contained in the paths of seismic waves.

As a rule, oceanic crust is subducted under the adjoining continent or under other oceanic crust at the major fault zones bordering and traversing the Pacific. Seismic waves generated by earthquakes and passing through the earth’s interior provide information about the underground structure of such regions, and with few exceptions they run according to specific patterns. Accordingly, the waves pass through an anisotropic region by splitting up and propagating at right angles to one another in two different directions and at two different velocities. In subduction zones, the fast component of shear waves alignes normally parallel to the trench. This is usually interpreted as due to flow of the mantle parallel to the trench in the region below the slab. However, numerical models show that the flow is perpendicular to the slab...