Terrestrial Tomography

To researchers who use Earth’s normal modes of oscillation to map the threedimensional structure of the planet’s interior, the good fortune of having the largest‐ever deep‐focus earthquake occur just after the deployment of global broadband seismographic networks seemed like a dream come true. It was certainly no dream, though, and computers have been crunching data ever since. Barbara Romanowicz, Xiang‐Dong Li and Joseph Durek (University of California, Berkeley) used normal modes excited by recent large deep‐focus quakes in Bolivia and elsewhere to characterize the anisotropy of Earth’s inner core. Michael Ritzwoller and Joseph Resovsky (University of Colorado at Boulder) and Jeroen Tromp and Xiong He (Harvard University) used data from several recent deep‐focus earthquakes to show that normal‐mode studies can yield improvements in three‐dimensional models of Earth, especially for the planet’s mantle