Determination of elastic thickness of the lithosphere using gravity and topography data: a case study for the Golpayegan, Arak, and the Qom Blocks

The elastic thickness, Te, is a measure of the strength of the lithosphere under loading and its elastic behavior. While there have been previous investigations on the nature of the lithosphere of Iran using satellite gravity and topography data, here, for the first time, using high-resolution gravity data we determine the elastic thickness for the Iranian lithosphere on a small scale, focusing on a region including Golpayegan, Arak, and Qom Blocks. The lithospheric elastic thickness is calculated using a wavelet transform method. The technique uses a superposition of two-dimensional Morlet wavelets that yields isotropic yet complex wavelet coefficients for the auto- and cross-spectra of gravity and topography data. These are subsequently applied to compute a spatially varying, isostatic coherence, from which both global and local estimates may be obtained. We applied the method to synthetic gravity and topography data generated for a thin elastic plate of uniform elastic thickness. After testing the validity of the technique on synthetic data, it was applied on real terrestrial gravity and topography data obtained from the National Cartographic Center (NCC) with grid spacing of 5 km. The average value calculated for the elastic thickness in the study area is 28 km which is in good accordance with the geological/tectonic structure of the region and previous interpretations for lithospheric strength based on geophysics and geodynamic studies.