Strength of the lithosphere derived by geological and geophysics data: the Graham Land (Antarctic Peninsula) case study

Abstract

We explore the strength of the lithosphere beneath the Graham Land region (Antarctic Peninsula) using numerical modeling which simulate lithospheric deformation as a function of geological and geophysical parameters. First, we process 21 GNSS time series data spanning 1997–2022 provided by the Nevada Geodetic Laboratory, to produce a robust tectonic velocity solution and calculate a new geodetic strain rate model using an optimal mesh grid definition of 0.5 x 0.5 degrees that best fits our study area. Second, we combine our new geodetic strain rate model with the Moho depth and rheological parameters such as geothermal heat flow (GHF), heat productions and thermal conductivity previously published in the literatures to determine yield strength envelope (YSE) along three profiles (A, B and C respectively) beneath Graham Land. The lithospheric strength values are in a range from 0 to 500 MPa and depend more on strain-rates at the surface and thermal regime (GHF) than on crustal thickness. The highest values for the crust (500 MPa) are mostly concentrated in the profile A, near Cape Alexander, where the second invariant of the strain rate present the smaller value (5-15 μstrain/yr) and the principal strain rates are compressive approximately in the N-S directions. In contrast, the highest values for the mantle mainly depend on the thermal structure of the lithosphere and Moho depth and the highest values are concentrated in the profiles B (297 MPa) and C (279 MPa), in the Trinity Peninsula. Here, the second invariant of the strain rates, present the larger value (50-80 μstrain/yr) and the principal strain rates are extensive in the W-E directions, with a maximum value of 30 μstrain/yr. The results of our study demonstrate that both “jelly sandwich” and “crème brûlée” models are valid for the Graham Land lithosphere, depending on specific thermal and rheological conditions considered.