At what stress level is the central Indian Ocean lithosphere buckling?

Internal contrasts in strength are responsible for lithospheric buckling. These are quantified by comparing the Indian Ocean data to two-dimensional visco-elasto-plastic numerical models where the material properties depend on temperature and pressure. The central Indian Basin is known for its intraplate seismicity and long wavelength undulations of the sea floor and associated gravity signatures. To simulate the amplitudes of undulations that reach 1 km within about 11 Ma of compression and 60 km of shortening, the required mean yield strength of the lithosphere is 400 MPa. If either a hydrostatic fluid pressure is considered in the crust or a mechanical decoupling at the depth of the Moho, small crustal wavelengths are superimposed on the long wavelength deformation, in agreement with observations. It is then possible to match the alternative indication that buckling commenced only 4 Ma ago, with a total amount of shortening of 30 km, and with a required yield strength of 200 MPa. About 10% of homogeneous thickening accompanies buckling. Taking into account variable thermal conductivity demonstrates that a change in the geotherm is sufficient to increase buckling amplitudes by 10% within 5 Ma. (C) 2000 Elsevier Science B.V. All rights reserved.