Global 1-D Earth models (original) (raw)

For many years the most widely used 1-D model of seismic velocities in the Earth has been the Preliminary Reference Earth Model (PREM) of Dziewonski and Anderson (1981). This model was designed to fit a variety of different data sets, including free oscillation center frequency measurements, surface-wave dispersion observations, travel-time data for a number of body-wave phases, and basic astronomical data (Earth ́s radius, mass, and moment of inertia). Table 1 summarizes, as functions of depth and Earth ́s radius, the PREM velocities vp and vs for P and S waves, the density ρ, the shear and bulk quality factors, Qμ and Qκ, and the pressure P. Note, that density and attenuation (~ 1/Q) are known less precisely than the seismic velocities but these parameters are required for computing synthetic seismograms. In order to simultaneously fit Loveand Rayleigh-wave observations, PREM is transversely isotropic between 80 and 220 km depth in the upper mantle. Transverse isotropy is a spheri...

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