preliminary reference Earth model

{{Short description|Model representing the average Earth properties as a function of planetary radius}}

File:EarthGravityPREM.jpg

The preliminary reference Earth model (PREM) plots the average of Earth's properties by depth.{{cite journal|last1=Dziewonski|first1=Adam M.|date=June 1981 |title=Preliminary reference Earth model |journal=Physics of the Earth and Planetary Interiors |volume=25 |issue=4 |pages=297–356 |url=https://www.cfa.harvard.edu/~lzeng/papers/PREM.pdf|doi=10.1016/0031-9201(81)90046-7 |last2=Anderson |first2=Don L. |bibcode=1981PEPI...25..297D}} It includes a table of Earth properties, including elastic properties, attenuation, density, pressure, and gravity.

PREM has been widely used as the basis for seismic tomography and related global geophysical models.{{cite book|last1=Dziewonski |first1=A. M. |last2=Romanowicz |first2=B.A. |title=1.01 - Overview|journal= Treatise on Geophysics |editor-first=Gerald |editor-last=Schubert |date=2007 |pages=1–29 |isbn=9780444527486 |doi=10.1016/B978-044452748-6.00001-8|bibcode=2007sse..book....1D }} It incorporates anelastic dispersion and anisotropy and therefore it is frequency-dependent and transversely isotropic for the upper mantle.

PREM was developed by Adam M. Dziewonski and Don L. Anderson in response to guidelines of a "Standard Earth Model Committee" of the International Association of Geodesy (IAG) and the International Association of Seismology and Physics of the Earth's Interior (IASPEI) Other Earth reference models include iasp91{{Cite book|title=IASPEI 1991 Seismological Tables|last=Kennett|first=B.L.N.|publisher=Bibliotech|year=1991|location=Canberra, Australia}} and ak135.{{Cite journal|last1=Kennett|first1=B. L. N. |last2=Engdahl |first2=E. R. |last3=Buland |first3=R. |date=1995-07-01 |title=Constraints on seismic velocities in the Earth from traveltimes |journal=Geophysical Journal International |volume=122 |issue=1 |pages=108–124 |doi=10.1111/j.1365-246X.1995.tb03540.x |issn=1365-246X |bibcode=1995GeoJI.122..108K|doi-access=free }}