Ionospheric earthquake precursors

Executive Summary

Anecdotal studies suggest that ionospheric disturbances sometimes occur as short-term precursors to earthquakes with a precursor time of several days. This study initiates an examination of possible ionospheric earthquake precursors in New Zealand, with a view to systematically testing their value for short-term earthquake forecasting.

GPSTk software produced by the University of Texas at Austin to compute Total Electron Content (TEC) in the ionosphere from GPS network observations has been adapted to the New Zealand region. It has been used to estimate the TEC in the ionosphere on a spatial grid of locations surrounding the New Zealand region for selected periods preceding and following four recent major earthquakes - the M7.1 2010 Darfield earthquake, M6.3 2011 Christchurch earthquake, M6.5 2013 Seddon earthquake and M6.6 2013 Lake Grassmere earthquake. The software gives snapshots of the spatial variation of TEC over New Zealand at 30-second intervals.