# How the elastic properties are distributed for a heterogeneous material?

**URL:** <https://community.geodynamics.org/t/how-the-elastic-properties-are-distributed-for-a-heterogeneous-material/3396>\
**Category:** PyLith\
**Created:** [April 10, 2024, 2:47am UTC](https://community.geodynamics.org/t/how-the-elastic-properties-are-distributed-for-a-heterogeneous-material/3396 "2024-04-10T02:47:08Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![juanpamerino](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/juanpamerino/32/1346_2.png) [@juanpamerino](https://community.geodynamics.org/u/juanpamerino)\
**Post date:** [April 10, 2024, 2:47am UTC](https://community.geodynamics.org/t/how-the-elastic-properties-are-distributed-for-a-heterogeneous-material/3396/1 "2024-04-10T02:47:08Z")

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Hello everyone,  
I have a mesh composed of four blocks, where one of them is the continental crust. For the latter I have a seismic tomography, so the elastic properties of the crust are heterogeneous. My question is if for example the horizontal extent of my continental crust is between 28-32°S and 72-65°W, but my tomography has an extent between 29-31°S and 70-68°W how is this distributed for the rest of the domain?.  
Just in case, I already implemented this for a quasi-static coseismic displacement and got consistent results.

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**Author:** ![baagaard](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/baagaard/32/615_2.png) [@baagaard](https://community.geodynamics.org/u/baagaard)\
**Post date:** [April 10, 2024, 3:37am UTC](https://community.geodynamics.org/t/how-the-elastic-properties-are-distributed-for-a-heterogeneous-material/3396/2 "2024-04-10T03:37:14Z")

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In general, the spatial database values are interpolated. If a spatial database finds that it is extrapolating, it will produce an error message and a PyLith simulation will abort. If you use a `SimpleDB` with the `query_type` set to `nearest` ([SimpleDB — SpatialData 3.1.0dev documentation](https://spatialdata.readthedocs.io/en/latest/user/components/spatialdb/SimpleDB.html#pyre-properties)), then throughout the entire region where the spatial database is used, the nearest values will be used, including along the boundaries; in this case the spatial database need not extend over the entire simulation region. If you want values interpolated from the tomography model, then I recommend padding values along the boundaries of your tomography model so that it spans the extent of the region where the spatial database is used. If the tomography model is a logical grid, then I recommend using the `SimpleGridDB` ([SimpleGridDB — SpatialData 3.1.0dev documentation](https://spatialdata.readthedocs.io/en/latest/user/spatialdb/simplegriddb.html)) as the queries are more efficient.