The study of the Earth’s interior is based upon the comparison of laboratory data on longitudinal and shear wave speeds of minerals with the seismic wave speeds from the Earth (see Fig. 1). This requires
laboratory measurements of the temperature- and pressure-dependence of single-crystal elastic moduli to be recast in terms of wave speeds and densities of polycrystalline materials of possible mantle compositions and mineralogies; together with
highly accurate information on seismic wave speeds as a function of depth in the mantle, together with
jumps in wave speeds due to phase transitions,
a temperature profile of the Earth,
a density profile of the Earth,
a pressure profile of the Earth, together with
a petrological model of the Earth as a function of depth.
While seismologists and petrologists have been acquiring their data, mineral physicists have been working on new, varied and imaginative methods of measuring wave speed first in single crystals, and more recently in polycrystalline materials at the temperature and pressure conditions of the Earth.
There are a range of different methods used to determine the speed at which stress waves travel through materials at high-pressure and temperature conditions (see Fig. 2). These methods include the following:
Shock wave measurements involve shooting a projectile at the sample of interest. The resulting collision creates high temperature, high pressure conditions within the sample, and the speed at which the shock wave travels through the sample is measured (e.g. Jackson & Ahrens, 1979; Watt & Ahrens, 1986; Luo et al., 2002; Panero et al., 2003; Langenhorst & Hornemann, 2005).