Conference / Tradeshow

ASEG Inversion Forum: The importance of inputs other than the data for geophysical inversion

August 10, 2013
1-5 Spencer St
Crowne Plaza Hotel - Bridge 2, Melbourne, Australia | Website

 

 

 

 

 

Geosoft Senior Scientist, Rob Ellis will discuss the importance of inputs to a geophysical inversion, other than survey data, which determines whether the inversion produces an earth model with real exploration value. This presentation will focus on these auxiliary inputs, highlighting their importance and suggesting strategies for their optimization. Examples of auxiliary inputs include:

  • Data errors: absolute vs. relative errors, error size, instrument error vs. modelling errors, data preprocessing: filitering, decimation, regional-residual seperation, trend removal.
  • Inversion mesh: type element sizes, padding cells, prism element terrain artefacts.
  • Depth weighting: explicit formulae, integrated sensitivities, tuning to local geology.
  • Reference models: parameter and gradient reference models, model weights.
  • Regulization parameters: choice of trade-off parameter, weighting various terms in the objective function.
  • Constraints: parameter bounds, positivity, geometric constraints, focusing, iterative reweighting, complementary survey data.

Even with the best auxiliary input parameter strategies, extensive industry experience with geophysical inversion has shown that it is necessary to be able to quickly and efficiently iterate through a number of auxiliary parameter scenarios to find the best combination for each geophysical survey. To do this in a real exploration workflow requires a very stable inversion and a robust and user friendly inversion interface that includes a record of all auxiliary inputs.

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