Estimates of the minimum 3-D stress in the lithosphere needed to support global topography
Abstract
Present-day topography was formed by complex tectonic and erosional processes acting over geologic timescales, so computing the present-day 3-D deviatoric stress in the global lithosphere is perhaps an impossible task. However, we can estimate the minimum deviatoric stress needed to support both the long-wavelength (greater than 600 km) geoid and the short-wavelength (less than 600 km) topography. The principal components of this global 3-D stress tensor are compared with the principal stress orientations recorded in the World Stress Map catalogue. The long-wavelength 2-D stress is computed by applying a body force, consistent with the gradient of the geoid, to an incompressible thin elastic shell; this is the standard gravitational potential energy approach (GPE). The short wavelength 3-D stress tensor is calculated using a model of a thick incompressible elastic plate loaded from above and below by the present-day observed short-wavelength topography and the present-day Moho shape. Moho shape is determined by comparing the thick plate flexural response to short-wavelength topography with gravity observations. For the 2-D case, it has been shown that the second invariant of deviatoric stress is minimized when the material is incompressible, and we show that this is also true for the 3-D stress. We find good agreement between the model and World Stress Map data both along the global mid-ocean ridge and along continental mountain fronts. The addition of the 3-D short wavelength topographic stress provides a significant reduction in rms misfit with respect to the 2-D GPE-only model. We are using this approach to assess the portion of the global tectonic stress that cannot be explained solely by the support of the geoid and topography.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.T51F..07L
- Keywords:
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- 8164 TECTONOPHYSICS / Stresses: crust and lithosphere