A New Global Crustal Model at 5x5 Degrees

Authors: Walter Mooney (USGS), Gabi Laske, Guy Masters

LAST UPDATE (September 06, 10): The anonymous ftp site for the model has moved and service was disrupted. The links to individual files have been re-opened.


We no longer update this model!
Updated versions on various scales can either be found on the USGS server or the UCSD server.
The UCSD server provides an improved 2x2 crustal model that uses the same philosopy as CRUST 5.1. For those of you who would like to reproduce earlier work, we will maintain this web site. But we strongly recommend to use CRUST 2.0 instead of CRUST 5.1.
(March, 2001)

Description of the model

The global crustal model uses a type key to assign crustal structure at a 5 x 5 deg scale. Data were gathered from seismic experiments and averaged globally for similar geological and tectonic settings (such as Archean, early Proterozoic, rifts etc.). These averages were used to assigned structure to regions without seismic information (e.g. most of Africa, South America). Ice and sediment thicknesses where gathered from published maps. Bathymetry and topography is that of ETOPO5. The global model is composed of 139 key 1d-profiles (the crustal types) where one of these profiles is assigned to each 5 x 5 degree cell.
Each individual profile is a 7 layer 1D-model with

  1. ice
  2. water
  3. soft sediments
  4. hard sediments
  5. upper crust
  6. middle crust
  7. lower crust

Parameters VP, VS and rho are given explicitly for these 7 layers as well as the mantle below the Moho.

Why do we need another crustal model?

Seismic tomography has been extensively used in various forms to determine the three-dimensional velocity structure of the Earth's mantle. The data used in these studies are surface wave (waveforms and dispersion measurements) and free oscillation (frequency shift) data as well as body wave travel times (arrival times from catalogues such as the ISC catalog and specially hand-picked long-period arrivals). For the majority of these studies, the crust has a significant impact on the observed seismic data but, at the same time, is too thin to be resolved by them. Most authors handle this by applying an assumed "crustal correction" to the data before an inversion for mantle structure. Since the inversion techniques can erroneously map crustal structure down to great depth (at least 250km), accurate crustal corrections to the data sets are extremely important.

Another aspect is the seismic monitoring of nuclear explosions. Key elements of the monitoring effort are location and size estimation. The location accuracy strongly depends on the chosen velocity model (i.e. crustal structure), especially when seismic sources lie outside the monitoring network.
Monitoring on regional scale includes the modelling of short-period surface waves and the propagation of Lg waves which are very sensitive to variations of crustal structure. Obviously, an accurate image of the Earth's crust would tremendously improve the understanding of wave propagation of such phases.

What makes our model so special?

Our crustal model differs from previous models in that:
Download postscript files.


W.D. Mooney, G. Laske and G. Masters, CRUST 5.1: A global crustal model at 5x5. J. Geophys. Res., 103, 727-747, 1998.
click here to download the model and Fortran source code to read the model.

Further info is available at the USGS site.

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