Salt marsh plant response to vertical deformation resulting from the February 2011 Christchurch earthquake

Investigations of modern coseismic ground surface deformation where fault rupture is absent typically rely on remote sensing techniques. We used monitoring of salt marsh vegetation and substrate for 3years after the 22 February 2011 Christchurch earthquake (M-W 6.2) to document the biological response to vertical deformation, to provide estimates of the amount of uplift and subsidence and ground-truth remote sensing data. Comparison of vegetation-derived vertical deformation with estimates from remote-sensing techniques (Light Detection and Ranging, Global Positioning System and Differential Interferometric Synthetic Aperture Radar) shows good agreement at sites where several decimetres of vertical movement occurred, and less agreement where smaller amounts of vertical movement occurred and/or where vegetation-monitoring sites were affected by differential movement of artificial structures such as roads and breakwaters. Biological and sedimentological changes observed in salt marshes around the Avon-Heathcote Estuary/Ihutai (AHEI) as a result of the 22 February 2011 Christchurch earthquake are likely to be preserved as subtle geological signatures in restricted locations around the AHEI.