“ringwoodite”

More complicated waves, too

Real life example

• At 23:24:50.6 GMT, on Nov. 22 2001, an earthquake occurred in Fiji (southwest Pacific)

• The P wave from this earthquake was recorded in Pasadena, CA at 23:36:50.7 GMT

• Therefore the observed travel time is 720.10 s• The distance between the Fiji earthquake and

the seismometer in Pasadena is 78.8o (8762 km).

• The theoretical (expected) travel time for a P wave at this distance is 721.25 s.

• Therefore the travel time residual is -1.15 seconds

Seismic stations from Fiji to the Tonga trench

Time residuals from Fiji across the Tonga trench

Inferred structure in one slice across the Tonga trench

Fiji Tonga

Pacific plate

earthquakes

slower P waves faster P waves

IMap of inferred structure 25 km down

140 km down

Earthquakes used to do global tomography and where the seismic stations are

A few random tomographic slices

Comparison of different tomographic reconstructions