How does this actually work:
Passive seismic methods use earthquakes as energy sources, and the resulting seismic waves are able to probe the whole planet. It is because of these methods that we know the general layering within our planet.
We record these seismic waves using three-component seismometers, which record ground motion in three perpendicular directions.
Earthquakes generate:
• body waves that travel through the Earth (P and S waves)
• surface waves that are confined to the near-surface layers of the Earth (Rayleigh and Love waves)
Seismic waves travelling through the Earth provide information about:
<> variations in seismic wave speed arising from temperature and
rock type
<> subsurface interfaces, such as:
- the base of the Earth's crust (also known as the Moho)
- the Lithosphere-Asthenosphere boundary (LAB)
- layering within the Earth's crust
- discontinuities within the Earth's mantle
- the Core-Mantle Boundary (CMB)
<> directional variations in seismic wave speed due to structural or
mineral alignments (also known as anisotropy)