Browsing by Author "Caravella, Letizia"

Cryoseisms are non-tectonic seismic events associated with freezing processes. They occur under specific conditions including frost, saturated ground, thin snow coverage, and rapid temperature drops. The recognition and study of ice quakes and frost quakes are of particular importance in Finland due to their potential impact on seismic catalogue reliability and their impact on the public, as it is documented that these events can be clearly felt and may cause damages in buildings and infrastructure. The open-source probabilistic earthquake source inversion framework Grond was employed to identify the source mechanism of cryoseisms through the computation of their seismic moment tensor. The catalogue includes 39 ice quakes and frost quakes recorded across Finland between 2006 and 2017 with magnitude range between -0.2 and 1.4. In order to perform the inversion and compute synthetic waveforms, Green’s functions were calculated and handled with Fomosto, a module of the Pyrocko toolbox. The optimisations tested two frequency ranges, 1-3 Hz and 2-4 Hz, and several spatial and temporal ranges for the source model space and the source-receiver configuration. Despite the efforts to refine the optimization parameters, the results exhibit considerable incongruity in the waveform fitting, the source location determination and the moment tensor decomposition obtained. None of the solutions would be reasonably compatible with the expected vertical fracture opening. The quality and reliability of the model solutions have been likely affected by the low signal-to-noise ratios of the observations and the network configuration, that is too sparse for the centroid moment tensor inversion of these seismic sources. The deployment of a more appropriate station network might provide a more robust dataset, allowing to constrain the seismic moment tensor parameters.