GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.3 GNGTS 2023 A MATLAB/GNU Octave toolbox for computation of velocity and strain rate field from GNSS coordinate time series G. Teza 1 , A. Pesci 2 , M. Meschis 3 1 Alma Mater Studiorum University of Bologna, Deptartment of Physics and Astronomy. 2 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna. 3 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo. Keywords: GNSS; Velocity; Crustal Kinematics; Crustal Deformations; Strain Rate Field. Abstract The time series of coordinates provided by a network of GNSS stations allow the calculation of the strain rate of an area in order to investigate the corresponding crustal tectonic deformations. For this reason, it is advisable to develop a toolbox aimed at calculating the strain rate with a high level of automation using time series available in data repositories (for example that of the Nevada Geodetic Laboratory, NGL, Blewitt et al., 2018), possibly supplemented by data obtained with other GNSS stations directly processed by the user. A MATLAB toolbox, also compatible with GNU Octave, was developed and tested for these purposes. The proposed toolbox consists of two components. The first one, StaVel, implements these steps: (i) time series download from a data repository (e.g. the NGL); (ii) calculation of the velocities of the selected stations by means of the Maximum Likelihood Estimation (MLE), Langbein (2004), method implemented in the external package Hector (Bos et al., 2013), including modeling of offsets, outliers, noise and periodic components; (iii) estimation of Common Mode Error and, if necessary, its removal from time series of some stations and recalculation of the corresponding velocities. The second component, GridStrain, is an evolution of grid_strain toolbox (Teza et al., 2008) and carries out these steps: (i) calculation of the strain rate field on a regular grid with the modified least squares method, in which a scale factor can be introduced to define the locality of the deformation analysis. Besides the strain rate field, the toolbox provides the corresponding uncertainty estimation and geometric evaluation of the significance of the results;