A note on estimating \(T_{e}\) from Bouguer coherence

Original Paper


The coherence between Bouguer gravity anomalies and topography is widely used to estimate the value of \(T_{e}\), the effective elastic thickness of the lithosphere. In areas where there is little topography but substantial free air gravity anomalies there is often little coherence between the free air anomalies and topography. In such regions the Bouguer coherence method generally gives estimates of \(T_{e}\) of 90 km or more. A detailed analysis shows that, under these conditions, the value of the Bouguer coherence \(\gamma ^2_b\) is entirely controlled by the ratio of the power spectra of the free air gravity anomalies and the uncompensated topography, and contains no information about the value of \(T_{e}\). What is worse, under these circumstances the variation of \(\gamma ^2_b\) with wavelength closely resembles that expected for large values of \(T_{e}\). These results show that neither the Bouguer coherence method nor the admittance method can produce meaningful estimates of \(T_{e}\) when the free air gravity anomalies are incoherent with the topography.


Bouguer coherence Effective elastic thickness 

Mathematics Subject Classification




I thank J. Jackson and F. Simons for their help and D. Forsyth for his detailed reviews.


  1. Banks, R.J., Parker, R.L., Huestis, S.P.: Isostatic compensation on a continental scale: local versus regional mechanisms. Geophys. J. Int. 51, 431–452 (1977)CrossRefGoogle Scholar
  2. Bechtel, T.D., Forsyth, D.W., Sharpton, V.L., Grieve, R.A.F.: Variations in effective elastic thickness of North American lithosphere. Nature 343, 636–638 (1990)CrossRefGoogle Scholar
  3. Forsyth, D.W.: Subsurface loading and estimates of the flexural rigidity of continental lithosphere. J. Geophys. Res. 90, 12623–12632 (1985)CrossRefGoogle Scholar
  4. Jackson, J., McKenzie, D., Priestley, K., Emmerson, B.: New views on the structure and rheology of the lithosphere. J. Geol. Soc. Lond. 165, 453–465 (2008)CrossRefGoogle Scholar
  5. Kirby, J.F.: Estimation of the effective elastic thickness of the lithosphere using inverse spectral methods: the state of the art. Tectonophysics 631, 87–116 (2014). doi: 10.1016/j.tecto.2014.04.021 CrossRefGoogle Scholar
  6. McKenzie, D.: Estimating \(T_{e}\) in the presence of internal loads. J. Geophys. Res. 108(B9), 2438 (2003). doi: 10.1029/2002JB001766 CrossRefGoogle Scholar
  7. McKenzie, D., Fairhead, J.D.: Estimates of the effective elastic thickness of the continental lithosphere from Bouguer and free air gravity anomalies. J. Geophys. Res. 102(B12), 27523–27552 (1997)CrossRefGoogle Scholar
  8. McNutt, M.K., Parker, R.L.: Isostasy in Australia and the evolution of the compensation mechanism. Science 199, 773–775 (1978)CrossRefGoogle Scholar
  9. Munk, W.H., Cartwright, D.E.: Tidal spectroscopy and prediction. Philos. Trans. R. Soc. Lond. Ser. A 259, 533–581 (1966)CrossRefGoogle Scholar
  10. Pérez-Gussinyé, M., Watts, A.B.: The long-term strength of Europe and its implications for plate-forming processes. Nature 436, 381–384 (2005). doi: 10.1038/nature03854 CrossRefGoogle Scholar
  11. Pérez-Gussinyé, M., Lowry, A.R., Watts, A.B.: Effective elastic thickness of South America and its implications for intracontinental deformation. Geochem. Geophys. Geosyst. 9, Q02003 (2007). doi: 10.1029/2006GC001511 Google Scholar
  12. Simons, F.J., Olhede, S.C.: Maximum-likelihood estimation of lithospheric flexural rigidity, initial-loading fraction and load correlation, under isotropy. Geophys. J. Int. 193, 1300–1342 (2013). doi: 10.1093/gji/ggt056 CrossRefGoogle Scholar
  13. Watts, A.B.: Isostasy and Flexure of the Lithosphere, p. 458. Cambridge University Press, Cambridge (2001)Google Scholar
  14. Zuber, M.T., Bechtel, T.D., Forsyth, D.W.: Effective elastic thickness of the lithosphere and the mechanisms of isostatic compensation in Australia. J. Geophys. Res. 94, 9353–9367 (1989)CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.Department of Earth SciencesBullard LabsCambridgeUK

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