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Abstract:
We retrieved source mechanisms in the moment-tensor description (MT) of an intense earthquake-swarm activity on the Reykjanes Peninsula (SW Iceland) in 2020 to 2021 preceding the Fagradalsfjall volcanic eruption in March 2021. We inverted displacement amplitudes of the direct P- and S-waves from a local network REYKJANET complemented the network of the University of Cambridge and by the near stations of the regional SIL network; a total of about 30 stations covering well the Fagradalsfjall are used. For a sufficient resolution of the source mechanism an accurate enough response of the medium the Green’s function (GF) is demanded. For this purpose we used a 1-D velocity model for the Reykjanes Peninsula by Vogfjörd et al. (2002). For the GF construction, we applied the ray theory. Substantial effort has been devoted to facilitate a batch processing of the events, first of all it means to allow the ANRAY to work in a semi-automatic regime, which is not its inherent mode of work. As a result, we have a comprehensive tool for retrieval of MTs on the Reykjanes Peninsula. We demonstrate its usefulness by treating a set of several tens of events. Source mechanisms of some of them are compared to those obtained by ISOLA, a software for processing of regional earthquakes, which however applies different data and different approach. Our set of MTs retrieved provides a deeper insight into the mechanism of faulting due to dyke propagation in the region in question from the beginning of 2020 to March of 2021.
