Improving Bahr's invariant parameters using the WAL approach

Anna Martí*, Pilar Queralt, Alan G. Jones, Juanjo Ledo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


In the magnetotelluric technique, several methods exist to perform dimensionality analysis of the measured data using rotational invariants of the impedance tensor. Among these methods there is some dilemma on the different criteria established, which sometimes lead to non-equivalent interpretations. The aim of this work is to compare the Bahr and Weaver et al. (WAL hereafter) methods, and to propose a new method that makes both dimensionality methods consistent. This new method complements the parameters used in Bahr method with WAL invariant Q, and redefines their threshold values. To accomplish this, we used the analytical relations between both sets of parameters and re-analyse and compare the threshold values of each method. Both the Bahr and WAL methods use sets of rotational invariant parameters of the magnetotelluric tensor [M(ms-1; E→ = M · B→] and establish a classification of their values to determine the kind of dimensionality associated to the measured data.

Original languageEnglish
Pages (from-to)38-41
Number of pages4
JournalGeophysical Journal International
Issue number1
Publication statusPublished - Oct 2005
Externally publishedYes


  • Geoelectric dimensionality
  • Magnetotelluric tensor
  • Rotational invariants
  • Threshold values


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