Near-field surface displacement of the 2016 Norcia & Kaikoura earthquakes measured using low-cost GNSS

The temporal evolution of coseismic and postseismic slip on surface ruptures is important to aid our understanding of earthquake physics, for assessing fault displacement, to help define seismic hazard and for predicting ground motion. However, measurements of near-field surface displacement at high temporal resolution are elusive. We present two novel records of near-field displacement with high temporal and spatial resolution from the 2016 30th October Mw 6.6 Norcia (Central Italy) and Mw 7.8 Kaikoura earthquakes measured using low-cost Global Navigation Satellite System (GNSS) receivers. In the case of the Norcia earthquake, we observe coseismic displacement and formation of the surface ruptures at 1-second temporal resolution with a clear temporal and spatial link between our near-field record and InSAR, far-field GPS data, regional measurements from the Italian Strong Motion and National Seismic networks, and field measurements of surface ruptures. The GNSS dataset illustrates that the surface ruptures formed through the propagation of slip from depth on a surface rupturing (i.e. capable) fault array as a direct and immediate response to the Norcia earthquake. A rise-time of 2 – 4 seconds and slip velocity of 0.13 – 0.52ms-1 are inferred from the data. A detailed preseismic and postseismic timeseries will also be presented. In the case of the Kaikoura earthquake, we present multiple detailed 90-day timeseries of postseismic near-field surface displacement from a network of six low-cost GNSS receivers installed in an area of complex surface rupturing where multiple faults meet. We demonstrate that low-cost GNSS is an accessible, cost-effective and accurate tool for monitoring capable fault arrays when installed as custom-made, short-baseline networks.