# Using tomography in SPECFEM2D

**URL:** <https://community.geodynamics.org/t/using-tomography-in-specfem2d/1228>\
**Category:** SPECFEM\
**Created:** [April 29, 2020, 12:46am UTC](https://community.geodynamics.org/t/using-tomography-in-specfem2d/1228 "2020-04-29T00:46:10Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![pasansherath](https://avatars.discourse-cdn.com/v4/letter/p/d2c977/32.png) [@pasansherath](https://community.geodynamics.org/u/pasansherath)\
**Post date:** [April 29, 2020, 12:46am UTC](https://community.geodynamics.org/t/using-tomography-in-specfem2d/1228/1 "2020-04-29T00:46:10Z")

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Hi there,

I am trying to use a tomography model to define the velocities and densities in my model for SPECFEM2D. I have been referring to both SPECFEM2D and SPECFEM3D manuals on how to do this, and I am getting a different error each time I run xmeshfem2D. Most of the time I am getting unrealistic values for Poisson’s ratio, and it crashes. The Vp and Vs values that are read in have values of -1 and 1 respectively.

Can someone share an example that uses a tomography file? It will be immensely helpful for a newbie.

Thanks very much