2D strain rate and ground deformation modelling from continuous and survey mode GNSS data in El Hierro, Canary Islands

Abstract

We present a study of the deformation pattern in El Hierro Island through the analysis of GNSS data from surveys carried out between 2015 and 2019 as well as continuous data. The last eruption in El Hierro occurred under the sea on the south rift, lasted from October 2011 to March 2012, and it was preceded by intense seismic activity and nearly 5 cm ground inflation. After this eruptive cycle, further magmatic intrusions were detected, from June 2012 to March 2014, associated to intense seismic swarms and inflation (about 22 cm of uplift). Nevertheless, these magmatic intrusions did not culminate in any eruption. Following these post-eruptive episodes, the seismic activity became less intense. Thus, for the period of this study, about 500 earthquakes with magnitude ranging from mbLG 2 to mbLG 3.9 were recorded, the ground deformation measured is of lower magnitude, still remaining a slight uplift trend in the GNSS stations up to 2017 and followed by a slight subsidence of about 1.5 cm between 2017-2019. Our purpose is to explain the ground displacements measured and the earthquake occurrence in terms of geodynamics and seismotectonic activity along the island, for the period 2015-2019. Firstly, we retrieved the geodetic velocities from the GNSS daily solutions. Secondly, we computed the 2D infinitesimal strain rates from the velocities through a triangular segmentation approach to map the deformation pattern along the respective GNSS surveys.