Comparative Analysis of Methods to Estimate Geodetic Strain Rates from GNSS Data in Italy

Our ability to estimate surface deformation rates in the Central Mediterranean has considerably enhanced in the last decade thanks to the growth of continuous Global Navigation Satellite System (GNSS) networks. Focusing on the Apennine/Alpine seismogenic belt, this area offers the opportunity to test the use of geodetic strain rates for constraining active tectonic processes and for seismic hazard assessments. Given the importance of geodetic strain rate models in modern hazard estimation approaches, however, one has to consider that different approaches can provide significantly different strain rate maps. Despite the increasing availability of GNSS velocity data, in fact, strain rate models can significantly differ, because of the spatial heterogeneity of GNSS station locations and inherent strategies in computing strain rates. Using a dense GNSS velocity dataset, this study examines three methods for estimating horizontal strain rates, described in the recent literature, and selected to represent approaches of increasing mathematical complexity. The advantages, drawbacks, and optimal settings of each method are discussed. The main result is an ensemble of strain rate models that enable the evaluation of epistemic uncertainties in seismicity rate models constrained by geodetic velocities.