We present constraints on the regional variations of the
seismic and mechanical thickness of the Australian
lithosphere. We infer the seismic thickness from a
waveform tomographic model of S-wave speed, and as
a proxy for the elastic thickness we use the wavelength
at which the coherence of surface topography and Bouguer
gravity drops below half of its long-wavelength
maximum. Our results show that on scales smaller than 1000 km the
relationship between the age of the crust and the
thickness of the lithosphere is more complicated than
longer-wavelength or global averages suggest. Recent
geochemical and geodynamical evidence for small-scale
secular variations of the composition and stability of
continental cratons further illustrates the complexity
of the age dependence of seismo-mechanical lithospheric
properties on regional scales.
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