Broken Hill 2017

GEOS3330 excursion to Broken Hill provided a new opportunity this year. For the first time since I started doing this excursion, it rained on the field area during the day. Not enough to make us stop, or worry too much about the dirt road and the creek… Also, with the rain some foliations became a lot easier to spot while other almost disappear.

 

Broken Hill panoramas

Panoramas from Double Schistosity


Updates on TecPIV

TecPIV is my MATLAB GUI package for calibration, correction of images of analogue models, correlation of images to get incremental and cumulative displacements and spatial derivatives. The code is explained in the paper:

Boutelier D. TecPIV – A MATLAB-based application for PIV-analysis of experimental tectonics. Comput Geosci 2016;89:186–99. doi:10.1016/j.cageo.2016.02.002.

A new version of TecPIV has been posted. You can get the files from bitbucket here in the dev branch. I will soon post a zip file of the whole new version on this page.

I suggest if you have a version of TecPIV already installed, you make a zip file of it so the new TecPIV folder and its content can be uniquely defined in your MATLAB path.

Here is the change log:

  • Use MATLAB vectorization instead of parfor for parallelisation of correlation. (faster)
  • Allows window deformation in multipass. (better for narrow features)
  • Window overlap fixed at 50% (better for multipass)
  • Eulerian and Lagrangian sums in the postprocessing menu. Lagrangian output shown as deformed grid instead of vectors.
  • Closing the main window using the button does the same as using the save and close function.
  • Closing the second window makes its content, and the window itself invisible instead of deleting the object.
  • Less warning messages.

Exploring the diffusion equation

While preparing a lab on heat diffusion, I thought it would be interesting to compute the diffusion of topographic relief using the same forward Euler finite difference in 2D (explicit method with central difference in space and forward in time, see here).

I downloaded a dem of largest topographic reflief on the planet, the Himalayas and roughly converted the lat/long into meters before applying the finite difference method. As expected, diffusion acts on the small scale features first, and especially those with large gradients… So the board topography remains but the details are progressively vanishing. Although it is incorrect for a landscape simulation, it is valuable to show the characteristics of diffusion.

In the second figure you can see the difference between the start and end stages and a few zoom-ins showing how material is diffused from the small (sic!), steep peaks to fill in the valleys.


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