PREM

PREM
AllenMcC. · CC BY 3.0 · source
Name	PREM
Full name	Preliminary Reference Earth Model
Field	Seismology; Geophysics
Introduced	1981
Creators	Adam Dziewonski; Don L. Anderson
Components	Radial profiles of density, seismic wave velocities, attenuation, anisotropy
Usage	Earth structure modeling, seismic tomography, geodynamics, planetary comparison

PREM

PREM is the Preliminary Reference Earth Model developed as a one-dimensional, radially symmetric standard for the internal structure of the Earth. It provides empirical profiles of density, compressional and shear seismic wave velocities, attenuation (Q), and anisotropy that serve as benchmarks for interpreting seismic observations from instruments operated by organizations such as the United States Geological Survey, International Seismological Centre, and research groups at institutions like Massachusetts Institute of Technology and California Institute of Technology. The model underpins comparisons among data from networks including Global Seismographic Network, Incorporated Research Institutions for Seismology, and satellite geodesy missions such as GRACE.

Overview

PREM presents spherically averaged radial profiles for the whole planet, dividing the Earth into concentric shells including the crust, mantle, outer core, and inner core. It is designed to reproduce travel times of body waves recorded in global catalogs compiled by entities like the International Seismological Centre and to be consistent with normal mode spectra from observatories such as Woods Hole Oceanographic Institution and Institut de Physique du Globe de Paris. The model is widely used alongside alternative models such as the IASP91 and regional references produced by groups at Stanford University and Cambridge University.

Structure and Composition

PREM gives quantitative radial distributions for parameters correlated with compositional and phase transitions identified by laboratory studies at facilities like the Carnegie Institution for Science and the Geophysical Laboratory. The mantle layering in PREM corresponds to seismic discontinuities associated with transitions examined in experiments at Lawrence Livermore National Laboratory and Oak Ridge National Laboratory, and aligns with mineralogical interpretations involving phases such as perovskite and post-perovskite. Core properties in PREM reflect constraints from high-pressure work at installations including Argonne National Laboratory and synchrotron studies at the European Synchrotron Radiation Facility, supporting a liquid outer core and solid inner core consistent with models developed by researchers at Scripps Institution of Oceanography and University of California, Berkeley.

Seismic and Geophysical Properties

PREM specifies compressional (P-wave) and shear (S-wave) velocity profiles that reproduce global travel-time datasets compiled by agencies like the National Earthquake Information Center and analyzed in studies published by journals such as Nature and Journal of Geophysical Research. The attenuation (Q) curves in PREM facilitate modeling of amplitude decay used by seismic tomography teams at ETH Zurich and University of Tokyo. PREM also includes a modest anisotropic parameterization of the inner regions, which has been compared to anisotropy detected in seismic splitting studies by groups affiliated with Columbia University and British Geological Survey. Its density profile is consistent with moment of inertia constraints derived from measurements by missions like LAGEOS and modeled by researchers at Jet Propulsion Laboratory.

Development and History

PREM was introduced in a landmark 1981 publication by Adam Dziewonski and Don L. Anderson while they were associated with institutions including Harvard University and the United States Geological Survey. The model synthesized global normal-mode analyses, body-wave travel-time inversions, and geodetic constraints accumulated in the mid-20th century by investigators at laboratories such as Carnegie Institution for Science, Lamont–Doherty Earth Observatory, and Seismological Society of America collaborations. Subsequent work by research teams at Massachusetts Institute of Technology, University of Cambridge, and Peking University has refined interpretation, produced variant parameterizations, and compared PREM to 3-D tomographic models from projects like GEOFON and regional compilations from Japan Meteorological Agency.

Applications and Uses

PREM serves as a standard reference for seismic waveform modeling used in earthquake source studies by the Southern California Earthquake Center and global moment tensor catalogs maintained by groups at Harvard–Smithsonian Center for Astrophysics. It is employed to build Green’s functions in waveform inversion workflows using software developed at Caltech and Stanford University, and underlies travel-time predictions used by tsunami early-warning centers such as those coordinated by the Intergovernmental Oceanographic Commission. Planetary scientists at organizations like NASA and the European Space Agency use PREM as a comparative baseline when interpreting seismic data from missions such as InSight and laboratory-derived equations of state. PREM informs geodynamic modeling of mantle convection pursued by researchers at Carnegie Institution for Science and Max Planck Institute for Geosciences.

Limitations and Criticisms

PREM’s one-dimensional, spherically symmetric nature omits lateral heterogeneity revealed by seismic tomography projects at University of Oxford and University of California, Santa Cruz, which detect anisotropy, plume-like upwellings, and subducted slabs that require 3-D models like those produced by SPECFEM and regional inversions from groups at Geoscience Australia. Critics at institutions such as MIT and Princeton University note that PREM’s averaged attenuation and anisotropy cannot capture frequency-dependent dispersion and scattering observed in arrays like USArray and networks run by Observatoire de la Côte d'Azur. Additionally, mineral physics studies at Bayerisches Geoinstitut and Swiss Federal Institute of Technology Zurich suggest compositional and phase complexities that require integrating PREM with mineralogical models and stochastic Earth models developed by consortia such as IRIS.

Category:Seismology models