Here, the seismic anisotropy of the Earth's lowermost mantle between North and Central America has been measured, using shallow and deep earthquakes to increase the azimuthal coverage. The findings show that the previously assumed vertical transverse isotropy — where wave speed should show no azimuthal variation — is not possible, and that more complicated mechanisms must be involved.
- Andy Nowacki
- James Wookey
- J-Michael Kendall