Data Services Newsletter

Volume 21 : No 3 : Winter 2019

EMC and Programmatic Access to the Earth Models

EMC repository growth.

The IRIS DMC’s Earth Model Collaboration (EMC) is a research community-supported long-term repository of Earth models created in 2011 to facilitate sharing, previewing, and accessing various Earth models. EMC’s Earth model repository currently includes over 70 Earth models (62 velocity, 3 crustal thickness, 7 electrical resistivity/conductivity, 1 attenuation, and 1 temperature) and 9 reference Earth models. The Earth model authors are encouraged to share their geophysical models with the research community through EMC (see EMC’s guidelines for model submission).

Model access and visualization Visualization

EMC’s model overview pages and DMC’s Searchable Product Depository (SPUD) model pages, contain information on individual models and provide direct access to model data and metadata under a uniform netCDF 3 format. Model format conversion from netCDF to and from text GeoCSV is possible using the publicly available Python emc-tools.

In addition to providing access to model data, metadata and references, EMC provides a set of web-based visualization tools to produce a variety of horizontal slices, vertical slices and velocity profiles for model preview. Users can further refine these plots by downloading the corresponding visualization bundle that includes both the model data and the Generic Mapping Tools plotting scripts.

EMC ParaView

Visualization of the Earth model in 3D is possible through a set of Python plugins (programmable filters/sources) for ParaView, an open-source data analysis and visualization application. These plugins allow users to interact with ParaView to visualize EMC or other netCDF/GeoCSV Earth models in 3D.

New: model access and visualization via web services

Programmatic access to the EMC’s contributed Earth models and reference Earth models is now possible through IRIS Earth Model Web Service. The service offers access, subsetting, or model information for EMC repository models through the following five endpoints (see the Earth Model Web Service Documentation):

  • /modelinfo—Produces a list (as plain text or JSON) of available Earth models along with a short summary for each.
  • /model—Provides data (in netCDF or GeoCSV format) for a model or a subset of a model via clipping and/or decimating.
  • /isosurface—Provides isosurface data (in netCDF or GeoCSV format) for selected variable(s) from a selected Earth model.
  • /plane—Provides data from a model (in netCDF, GeoCSV format, or as an image) by intersecting the model with a plane.
  • /line—Provides data from a model (in netCDF, GeoCSV format, or as an image) by intersecting the model with a line.

Like all other IRIS DMC web services, irisws earth-model service uses standard HTTP protocol technologies and can be accessed programmatically with a wide range of programming languages (e.g. Python, Perl, Java), command line utilities such as wget and curl or with any web browser with URL identifying the model parameters that you want to operate on. For example, getting a summary list of all available shear wave velocity models (variable=vs) that intersect the region between 25 and 57 degrees latitude (minlatitude=25&maxlatitude=57) is as simple as:

http://service.iris.edu/irisws/earth-model/1/modelinfo?variable=vs&minlatitude=25&maxlatitude=57&nodata=404

webservice
Portion of the modelinfo endpoint output providing a summary list of all available shear wave velocity models (variable=vs) that intersect the region between 25 and 57 degrees latitude (minlatitude=25&maxlatitude=57).

With this information at hand, you may now use the model endpoint to subset the CASCADE.ANT.GAO-SHEN.2014 model between 30° and 40° latitude and request the output in GeoCSV format.

http://service.iris.edu/irisws/earth-model/1/model?model=CASCADE.ANT.GAO-SHEN.2014&minlatitude=30&maxlatitude=40&format=geocsv&nodata=404

Or, alternatively, use the plane endpoint to plot (format=png) a slice of the model at the depth of 94 km to reproduce a similar slice from Gao and Shen (2014) of the CASCADE.ANT.GAO-SHEN.2014 model.

http://service.iris.edu/irisws/earth-model/1/plane?model=CASCADE.ANT.GAO-SHEN.2014&depth=94.0&minlat=39&maxlat=49&minlon=-125&maxlon=-110&format=png&nodata=404

slice
left: Gao and Shen (2014), shear-wave velocity structure (in km/s) at the depth of 94 km;
right: a slice of the CASCADE.ANT.GAO-SHEN.2014 model at the depth of 94 km using
the plane endpoint.

For additional information on all available query parameters for each endpoint, refer to the Earth Model Web Service Documentation.

With availability of such service, we anticipate a new generation of tools that display models or perform calculations based on models to be developed.

References

Gao, H., and Y. Shen (2014), Upper mantle structure of the Cascades from full-wave ambient noise tomography: Evidence for 3D mantle upwelling in the back-arc, Earth Planet. Sci. Lett., 309, 222-233, doi:10.1016/j.epsl.2014.01.012.

by Manoch Bahavar (IRIS Data Management Center) and Mick Van Fossen (IRIS DMC)

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