velocityconversion 1.1.2

Conversion of seismic velocities to temperature and density

VelocityConversion

• VelocityConversion
  • Introduction
  • Getting started
    • Use the latest version not on PyPI
  • Usage as command line tool
  • Usage as a Python module
  • Modifying physical properties of the minerals
  • Contributing
  • Citing
  • References
  • Licence

Introduction

This code is a python implementation of the p- and s-wave velocity to density conversion approach after Goes et al. (2000). The implementation was optimised for regular 3D grids using lookup tables instead of Newton iterations.

Goes et al. (2000) regard the expansion coefficient as temperature dependent using the relation by Saxena and Shen (1992). In VelocityConversion, the user can additionally choose between a constant expansion coefficient or a pressure- and temperature dependent coefficient that was derived from Hacker and Abers (2004).

For detailed information on the physics behind the approach have a look at the original paper by Goes et al. (2000).

Getting started

VelocityConversion requires Python 3 and numpy. Install numpy and VelocityConversion by running

pip install numpy velocityconversion

To uninstall VelocityConversion, run

pip uninstall velocityconversion

Use the latest version not on PyPI

If you want to use the very latest version, or want to contribute, clone the repository to you local hard drive:

git clone https://github.com/cmeessen/VelocityConversion.git

or, if you haven an SSH key associated to your account:

git clone [e-mail]:cmeessen/VelocityConversion.git

To check whether everything is working run the tests

python test.py

If the output looks like this, everything is working fine:

test_vp_AlphaConst (__main__.TestVelocityConversion) ... ok
test_vs_AlphaConst (__main__.TestVelocityConversion) ... ok
test_vs_AlphaPT (__main__.TestVelocityConversion) ... ok
test_vs_AlphaT (__main__.TestVelocityConversion) ... ok

----------------------------------------------------------------------
Ran 4 tests in 1.633s

OK

Usage as command line tool

In order to use the code as command line tool, add the ./Examples directory to your PATH, e.g. in your bash profile:

export PATH=/path/to/VelocityConversion/Examples:$PATH

Alternatively you can move the bash script VelocityConversion to a place that is within your PATH. Now the bash script VelocityConversion can be executed:

VelocityConversion

Usage: VelocityConversion FileIn -type <P|S> [optional args]
    Optional arguments:
        -AlphaT
        -AlphaPT
        -dT <val>
        -comp <Filename>
        -h | --help
        -NN
        -out <FileOut>
        -scaleV <value>
        -setQ <1|2>
        -v | -verbose
        -XFe <val>
        --version

The steps to prepare a conversion are

• definition of mantle rock composition in a *.csv file using the mineral terminology of MinDB.csv
• provide a velocity distribution on a regular 3D grid where columns are x y z v
• run VelocityConversion specifying the velocity type with -type P or -type S

Working examples for the usage as command line tool are provided in the script RunExamples.sh.

Usage as a Python module

VelocityConversion can also be imported as a Python module. Therefore, navigate to the folder that contains your clone of the repository (and setup.py) and execute

pip install -e .

Now, the module can be imported to Python:

from VelocityConversion import MantleConversion
MC = MantleConversion()

A short working example for a conversion is:

from VelocityConversion import MantleConversion
MC = MantleConversion()
MC.LoadFile("./Examples/VsSL2013.dat")
MC.SetVelType("S")
MC.DefaultMineralogy()
MC.FillTables()
MC.CalcPT()
MC.SaveFile("./Examples/VsSL2013_out.dat")

For a more complete documentation on how to use VelocityConversion as a Python module please visit the documentation.

Modifying physical properties of the minerals

The database that contains the physical properties of the individual mineral phases is stored in MinDB.csv. Mineral parameters can be edited, or new minerals added. A new mineral phase should then be referred to in the code or the assemblage file using the name that was assigned in the phase column of MinDB.csv.

Contributing

Please see CONTRIBUTING.md if you want to contribute to VelocityConversion.

Citing

If you use this code, please consider citing it as

Meeßen, Christian (2019): "VelocityConversion (v1.1.2)". Zenodo, http://doi.org/10.5281/zenodo.5897455.

or refer to CITATION.cff.

References

Berckhemer, H., W. Kampfmann, E. Aulbach, and H. Schmeling. “Shear Modulus and Q of Forsterite and Dunite near Partial Melting from Forced-Oscillation Experiments.” Physics of the Earth and Planetary Interiors, Special Issue Properties of Materials at High Pressures and High Temperatures, 29, no. 1 (July 1, 1982): 30–41. doi:10.1016/0031-9201(82)90135-2.

Goes, S., R. Govers, and P. Vacher. “Shallow Mantle Temperatures under Europe from P and S Wave Tomography.” Journal of Geophysical Research 105, no. 11 (2000): 153–11. doi:10.1029/1999jb900300.

Hacker, Bradley R., and Geoffrey A. Abers. “Subduction Factory 3: An Excel Worksheet and Macro for Calculating the Densities, Seismic Wave Speeds, and H2O Contents of Minerals and Rocks at Pressure and Temperature.” Geochemistry, Geophysics, Geosystems 5, no. 1 (January 1, 2004): Q01005. doi:10.1029/2003GC000614.

Kennett, B. L. N., E. R. Engdahl, and R. Buland. “Constraints on Seismic Velocities in the Earth from Traveltimes.” Geophysical Journal International 122, no. 1 (July 1, 1995): 108–24. doi:10.1111/j.1365-246X.1995.tb03540.x.

Saxena, Surendra K., and Guoyin Shen. “Assessed Data on Heat Capacity, Thermal Expansion, and Compressibility for Some Oxides and Silicates.” Journal of Geophysical Research: Solid Earth 97, no. B13 (Dezember 1992): 19813–25. doi:10.1029/92JB01555.

Schaeffer, A. J., and S. Lebedev. “Global Shear Speed Structure of the Upper Mantle and Transition Zone.” Geophysical Journal International 194, no. 1 (July 1, 2013): 417–49. doi:10.1093/gji/ggt095.

Sobolev, Stephan V., Hermann Zeyen, Gerald Stoll, Friederike Werling, Rainer Altherr, and Karl Fuchs. “Upper Mantle Temperatures from Teleseismic Tomography of French Massif Central Including Effects of Composition, Mineral Reactions, Anharmonicity, Anelasticity and Partial Melt.” Earth and Planetary Science Letters 139, no. 1–2 (März 1996): 147–63. doi:10.1016/0012-821X(95)00238-8.

Licence

Licence: GNU General Public Licence, Version 3, 29 June 2007

Copyright (2017): Christian Meeßen, Potsdam, Germany

VelocityConversion is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. VelocityConversion is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a cop y of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.