• seismic interferometry;
  • body wave;
  • seismic hum

Driven by oceanic and atmospheric waves and turbulence and their interactions with the surface and the sea floor, the Earth produces a low-frequency song known as “seismic hum,” a regular background hiss of seismic waves. By applying a mathematical technique known as cross-correlation interferometry to the observations of seismic hum produced by surface seismic waves, researchers have been able to better understand the structure and composition of the surface layers of the Earth's crust. Recently, researchers have started applying cross-correlation interferometry to seismic body waves, waves that travel through the Earth rather than along the surface to study the properties of Earth's mantle and core.