CRUST 2.0 a global crustal model at 2 x 2 degrees updates: ------- this model is a significantly updated version of CRUST 5.1. It takes advantage of our digital sediment map that is defined on a 1x1 degree grid. This new model also takes advantage of our still ongoing compilation of new data on crustal structure (a preliminary version for Eurasia can be found on the anonymous ftp site of CRUST 5.1, pub/gabi/crust). The ice thickness in CRUST 5.1 also was adjusted to better match the true ice thicknesses. The agreement is now to within 250m. We hope this model is of use in a large community and it will grow with every feedback. short description: ----------------- The global crustal model uses a type key to assign crustal structure at a 2 x 2 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 360 key 1d-profiles (the crustal types) where one of these profiles is assigned to each 2 x 2 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 and 7) lower crust. Parameters VP, VS and rho are given explicitly for these 7 layers as well as the mantle below the Moho. the files: --------- the model consists of three files: a) CNevelvatio2.txt: this is bathymetry and topography b) CNtype2.txt: this is the global model c) CNtype2_key.txt: this is the file with the profiles a) and b) are given tile by tile from -180 to 180 deg longitude and 90 - -90 deg latitude. The first number is for the tiles with midpoint 89N, -179E, the second one is 89N -177E, aso, and the last one is the one with 89S, 179E. suggested reading routine: ------------------------- readCN2-t7.f and readCN2-7vr.f are FORTRAN code which reads the model and give out maps of topography of the boundaries (readCN2-t7.f) and the seismic velocities and density (readCN2-7vr.f). The output maps are 180x90 numbers now going from 0 to 360 deg E (first number is at 89N, 1E!). The reading routines should also give out some other maps such as global topography in km, sediment thickness, ice thickness, total crustal thickness (where bathymetry is included). REMEMBER: Water and ice layer are flipped after this routine so that water now is layer 1 and ice layer 2. There will be 8 boundary maps, the first (map.t0) is top of water, while all the others define the bottom of the layers: map.t1: bottom of water map.t2: bottom of ice map.t3: bottom of soft sediments map.t4: bottom of hard sediments map.t5: bottom of upper crust map.t6: bottom of middle crust map.t7: bottom of lower crust=MOHO. These maps are all real topography, i.e. the depth with respect to sea level, not with respect to the actual surface. Therefore, map.t7 and map.thick (actual crustal thickness) are not the same! A routine which returns the model at a given location (interactive input) is getCN2point.f. On a UNIX machine, don't forget to compile the code: e.g. for getCNpoint f77 getCNpoint.f -o getCNpoint IMPORTANT NOTE ON THICKNESS OF THE WATER LAYER: ----------------------------------------------- the water thicknesses given in c) are only crude estimates and are not to be used in the model! Routine readCN2-t7.f replaces the water thickness with the true bathymetry (averaged to 2x2 degrees). Routine getCN2point returns the elevation/bathymetry. It replaces the water thickness in the 7-layer column by this value automatically. The crustal thickness is the thickness of the crust without the water layer. -------------------------------------------------------------------- references: ---------- If you use this model, please refer to the REM web site: http://mahi.ucsd.edu/Gabi/rem.html or Bassin, C., Laske, G. and Masters, G., The Current Limits of Resolution for Surface Wave Tomography in North America, EOS Trans AGU, 81, F897, 2000. A description of CRUST 5.1 can be found in: Mooney, Laske and Masters, Crust 5.1: a global crustal model at 5x5 degrees, JGR, 103, 727-747, 1998. A reprint can be requested: mooney@andreas.wr.usgs.gov (glaske@ucsd.edu, gmasters@ucsd.edu) related web sites: ------------ the crustal model is on the web: http://mahi.ucsd.edu/Gabi/crust2.html the 1x1 degree sediment map is on: http://mahi.ucsd.edu/Gabi/sediment.html the crustal model CRUST 5.1 is on: http://mahi.ucsd.edu/Gabi/crust.html if you use the anonymous ftp from there, simple save the files onto your machine (don't print them into a file!). new on public demand: -------------------- there is a little fortran routine called map2gmt. This routine asks for the name of one of the map. files. (e.g. map.t1). The output file is a .gmt file (e.g. map.t1.gmt). This file can be used in GMT (xyz2grd and then grdview/grdcontour?) to plot the maps. Gabi Laske