A New Global Crustal Model at 1x1
Gabi Laske, Zhitu Ma, Guy
Masters and Michael Pasyanos (LLNL)
UPDATE (August 26, 15): Dr. Zhu and his group provides new platform-independent, easy-to-use visualization tools for CRUST1. Go to visualization section.
UPDATE (August 27, 14): XYZ files of crustal and sediment thickness now available as separate files. Go to ready files.
UPDATE (November 16, 13): Surface wave code to calculate predictions for LITHO1.0 now provided. Go to LITHO 1.0 section for explanation.
UPDATE (August 27, 13): Model update. Go to updates for explanation.
UPDATE (August 20, 13): Created "External links" section. Please contact Gabi for
additional links that are useful to others.
UPDATE (August 16, 13): CRUST1.0 types released in add-on tar file. Please go to the download section for more info and the link to download the add-on.
UPDATE (July 15, 13): CRUST1.0 is now released. Please go to the download section for more info
and the link to download the model.
Please go to the reference section for a suitable citation and the 2013 EGU poster.
UPDATE (May 31, 13): We are really close to release. Please check back within the
next few weeks.
UPDATE (April 2, 12): We are currently modifying our CRUST1.0
proto-type model after testing revealed some inconsistencies with recent surface wave data.
We expect release by August 2012. A handout of the 2012 EGU
poster can be downloaded here.
Description of the model
This new model is specified on a 1x1 degree grid and incorporates an updated version of our
global sediment thickness
Bathymetry and topography is that of ETOPO1 that can be downloaded at NOAA's NGDC.
ETOPO1 is a 1-arc minute model of Earth's global relief, including surface topography and seafloor bathymetry. In ice-covered regions, "ice surface" and "bedrock" are given. From the ETOPO1 files, we derived topography, bathymetry and ice thickness in our new model by binning and averaging the ETOPO1 data in 1-degree cells.
The global crustal models CRUST5.1 and CRUST2.0 use type keys to assign
types of crustal structure (such as Archean, early Proterozoic, rifts etc.)
in each cell. In both these models, the crustal types were also used to assign
ice, sediment and crustal thickness.
In CRUST1.0, the principal crustal types are adopted from CRUST5.1. But the crustal types are now aligned with the crustal age map of Artemieva and Mooney. Additional crustal types mark specific tectonic settings, such as orogens, continental rifts, continental shelves and oceanic plateaus. CRUST1.0 also has a few new types, including one for very young (< 3 Myrs) oceans. In contrast to older models, the function of crustal types in CRUST1.0 is limited to assigning elastic parameters to layers in the crystalline crust.
CRUST1.0 will consist of less than 40 crustal types. Each of the 1x1-degree cells will have a unique
8-layer crustal profile where the layers are
Parameters VP, VS and rho are given explicitly for
these 8 layers as well as the mantle below the Moho. The parameters below the Moho are determined using a modified version of the recent Pn model LLNL-G3Dv3 (for the LLNL model, see below under external links).
- upper sediments
- middle sediments
- lower sediments
- upper crust
- middle crust
- lower crust
Global, Continental and Oceanic average
PREM reference: Dziewonski, A.M. and Anderson, D.L., 1981. Preliminary reference Earth model. Phys. Earth Planet.
Int., 25, 297-356.
Why do we need an accurate 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.
With the volume of datasets
and the demand on resolving small-scale structures increasing, we found
that the 2x2 degree model CRUST2.0 is no longer accurate enough.
27 August 2013
|The assignment of the continent/ocean boundary, was still loosely coupled to crustal types. In 136 cells along the
coast, this erroneously led to the omission of water. The crustal profile then started below sea level after the
bathymetry in ETOPO1 was added. In 7 cells, this meant a shift of 500 to 1140 m (see affected areas in the plot on the right).
We now add ETOPO1 directly into the model (see below under downloads).
Three areas are forced to NOT have water even though they are below sea level:
Caspian Depression (several cells), Qattara Depression in Egypt (1 cell), Lake Eyre in Australia (1 cell). NB: The Dead Sea and Death Valley
are both surrounded by high topography and therefore do not show up in CRUST1.0 as depressions.
The consequence of this change is that some costal areas now appear to be flooded even though the majority of the
area within a 1-degree cell is land. This is because the average topography is negative. The change is minor, and we retain the name and
version of the model.
The model and Fortran source code to read it is available here.
The Fortran source code should compile with any Fortran 77 compiler.
To download the compressed tar file, Click here. Use
gzip and then tar to extract the README, model files and 3 Fortran 77 routines. We expect to provide other software shortly.
For add-on that includes crustal type file Click here. Use gzip and then tar to extract readme-addon, 2 model files and a Fortran 77 routine similar to getCN1point.f.
Files ready for individual download:
Here are some most-widely requested files in various formats ready for individual download:
- Compressed xyz file of total crustal thickness (excl. water): click here
- Compressed xyz file of depth to Moho (with resp. to sea level): click here
- Compressed xyz file of sediment thickness (in km): click here
- Compressed xyz file of sediment thickness (in meters): click here
at http://www.visualearth.org/globalcrust10/crust10web/help/visualcrustdemo.rar. Download the compressed VisualCrustDemo.rar onto your computer and unzip, you will see the demo file: VisualCrustDemo.avi. Open the file you can see how VisualCrust works. Please find more info at VisualCrust website:
LITHO 1.0 section:
The model, input data, and some accompanying computer code will be distributed from here as we assemble and publish them.
Please follow this link to the surface wave section on the LITHO1.0 page
or this link to the top of the LITHO1.0 page.
References for the model:
Please refer to the REM web site if you use this model:
http://igppweb.ucsd.edu/~gabi/rem.html or to
Laske, G., Masters., G., Ma, Z. and Pasyanos, M., Update on CRUST1.0 - A 1-degree Global Model of Earth's Crust,
Geophys. Res. Abstracts, 15, Abstract EGU2013-2658, 2013.
A handout of the 2013 EGU poster can be downloaded here
Artemieva, I.M. and Mooney, W.D., Thermal thickness and evolution of
Precambrian lithosphere: A global study, J. Geophys. Res., 106, 16,387 - 166, 414, 2001.
CRUST 2.0 was introduced in a 2000 AGU poster. The abstract is:
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.
Links to older models CRUST5.1 and CRUST2.0
Though we do not encourage to use the older models CRUST5.1 and CRUST2.0, the pages
for these models will remain active without being updated.
Link to CRUST5.1
Link to CRUST2.0
20 August 2013: A group at the Sandia and Los Alamos National Laboratories develop 3D tomographic models of the crust and mantle. As part of this, the group developed a model parameterization on software support library for 3D Earth models. Their software distribution now includes CRUST1.0. Please find more info
at their GEOTESS website at www.sandia.gov/geotess.
Simmons, N.A, S.C. Myers, G. Johannesson and E. Matzel (2012), LLNL-G3Dv3: Global P wave tomography model for improved regional and teleseismic travel time prediction, J. Geophys. Res., 117, http://dx.doi.org/10.1029/2012JB009525.
Download the LLNL-G3D model from the IRIS website:
This research has been fully or partially funded through the following NSF grants: EAR-03-36864; EAR-12-15542; EAR-14-15763
Go back to
REM Crust page
Gabi Laske ( email@example.com)
Gabi's home page
Guy's home page