We have put together a compilation of geoscientific datasets that can be found on the web, they represent a subset of the datasets that are supported by iGMT. In addition to giving the links to outside sources we also provide original grd files that were generated from plate motion Euler poles and spherical harmonic coefficients of potential fields.

The iGMT project's earth science dataset collection

The following datasets are a small subset of geoscience data that is available on the web. (There are numerous webpages containing meta-data and link collections such as UNAVCO's Voyager site or Seismo surfing the internet.) Here, we only list some of the datasets that are directly supported by our mapping interface iGMT. Also note that some of the grid files such as geopotential and plate velocity datasets contain original, processed data based on Euler poles, spherical harmonic coefficients and the like. If appropriate, the copyright remains with the iGMT authors.

• Topography
  • The world-wide 5 degree topography dataset ETOPO 5 of NOAA (1988) is documented on the ETOPO 5 web page, (FTP here).
  • World wide topography based on gravity and GTOPO 30 in 30 second resolution by Sandwell and Smith (1997) can be found at the GTOPO 30 web page (FTP here, topo_6.2_img)
  
  
  
• Earthquake data
  • Harvard Central Moment Tensor solutions for a global database of focal mechanism of large earthquakes world wide (choose "GMT psvelomeca input")
  • NOAA significant earthquakes (Seach form here)
  • PDE earthquake catalog from NEIC
  • Sambridge & Gudmundsson (1998) slab seismicity contours
  
  
  
• Gravity/potential data
  • Datasets based on the EGM360 Potential model
    The EGM360 model consists of spherical harmonic coefficients for the geoid up to degree and order 360 and is a mixed solution using satellite and gravity measurements. We have expanded the coefficients in two ways:
    • Correcting for observed ellipticity: the Earth's observed flattening can be approximated by spherical harmonics of C_20 and C_40 (J_2=1.0826652e-3, J_4=-2.3492015e-6, compare Stacey 1992, p. 91). The fully (up to 360) expanded geoid with respect to this refernce ellipsoid is provided in a one degree resolution grid file (262kB). (GIF image here.) The long wavelength component (up to degree and order 16) can be found in the long wavelength grd file (262kB). (GIF image here.)
    • Correcting for the hydrostatic shape: Nakiboglu (1982) has shown that the equilibrium shape that is to be expected for a 'realistic' Earth which is hydrostatically flattening can be approximated by correction terms J_2=1.07270e-3 and J_4=-2.992e-6. The differences between these terms and the two above are 'real', that is related to dynamic processes and should be considered as part of the signal. This geodynamically more relevant geoid was expanded up to degree and order 360 (download one degree resolution grid file here (262kB) (GIF image here.) or a half degree resolution grd file here (1.1MB)(GIF image here.)), and up to degree and order 16 (download one degree res long wavelength grid here, 262kb). (GIF image here.)

    Units for all geoid undulation files are meters. All GIF images show geoid contours in 10m intervals and have NUVEL-1 plate boundaries in red as well as continental outlines in white as an overlay.

  • We can also convert the EGM360 geoid model into the gravity anomaly, since coefficients of the latter can be obtained by multiplying coefficients of the former by (l+1)/R, where l is the order of the expansion, and R the radius of the Earth. We have performed this conversion based on the ellipticity corrected geoid, and you can download the freeair gravity anomaly based on the EGM360 geoid in half degree resolution here (1.04MB). Units are mGal.
  • Sandwell free-air gravity field on oceans (FTP here, world_grav.img.7.2)
  • OSU91A geoid model from Ohio University (Rapp et al. 1991). Geoid model corrected for the observed ellipticity. We provide a 30 arc second gridded version, osualf91.0.5.grd, which is 1.1MB big for download.
  
  
  
• Plate motions

  We provide grd files with expanded plate velocities which are based on the NUVEL1 plate geometry model (DeMets et al., 1990) and various Euler poles as listed below. All files have 1 degree resolution, units are cm/yr, and the file size is 260kB each. For the Euler poles that went into this expansion, see, for example, the DGFI's listing of plate motion models, or the plate motion calculator by Tamaki.

  • NUVEL1 velocities in the no net rotation (NNR, toroidal l=1 modes are zero) reference frame from Argus and Gordon (1991). Download the grd file with the vx component and the vy component.
  • HS2-NUVEL1 velocities in the hotspot reference frame HS2 from Argus and Gordon (1991). Download the grd file with the vx component and the vy component.
  • NUVEL1 velocities with Eurasia held fixed obtained from DeMets et al. (1990). Download the grd file with the vx component and the vy component.
  • updated NUVEL1A velocities in the NNR reference frame from DeMets et al. (1994). Download the grd file with the vx component and the vy component.
  
  
  
• Other datasets
  • Müller seafloor ages (FTP here)
  • Smithsonian volcanism data (included in the full iGMT distribution)
  • Sediment thickness by Laske & Masters (1997). We provide their original data of 1 by 1 degree gridded sediment thicknesses as a GMT gridfile (200kB, use "shift-left mouse button" to download). Furthermore, we have interpolated the original values from the (0.5/1/359.5,-89.5/1/89.5)-format to a more convenient, slightly redundant (0/1/360,-90/1/90)-format, download the smoothed grid here (also 200kB).
  • World Stress Map data by Zoback (1992) and Mueller et al. (1997). iGMT v > 1.1 reads directly the csv-format found at the Karlsruhe server, for the gzipped csv data click here.
  • Global Seismic Hazard Assessment Program (GSHAP): A global, on-land 6 minute compilation of probabilistic estimates of expected ground shaking as documented in the GSHAP report. We provide a plotting facility for this type of data, the grid file can be obtained from the GSHAP Regional Center 3's web page: under "Final Results".
  • Seismic tomography: You might also be interested in the comparison of seismic tomography and geodyanmic mantle models by Becker & Boschi, see this link for additional online material or refer to the G-Cubed article.