Twentieth century constraints on sea level change and earthquake deformation at Macquarie Island

A rare combination of historical sea level observations from Sir Douglas Mawson's 1911–1914 Australasian Antarctic Expedition and modern data reveals a surprising land subsidence rate at Macquarie Island, contradicting geological evidence of long-term uplift. The study estimates relative sea level rise at +4.8 ± 0.6 mm/yr, suggesting the island is sinking despite geological uplift over millennia. Analysis of GPS data from 2000–2009 refines the source parameters of a 2004 Mw∼8.0 earthquake and infers an asthenospheric viscosity of 3×10^19 Pa s, providing insights into the island's tectonic evolution. The findings also indicate that ongoing viscoelastic relaxation from a 1924 earthquake contributes significantly to vertical deformation, with absolute sea level change estimated at +2.0 ± 0.8 mm/yr over the twentieth century, aligning with global averages.

Watson, C., Burgette, R., Tregoning, P., White, N., Hunter, J., Coleman, R., Handsworth, R., & Brolsma, H. (2010). Twentieth century constraints on sea level change and earthquake deformation at Macquarie Island. Geophysical Journal International, 182(2), 781–796. https://doi.org/10.1111/j.1365-246x.2010.04640.x