Noise-based monitoring of the hydrological discharge cycle in the South-Eastern Alps region, Italy

Seismological observations play a strategic role in the study of the temporal evolution of the mechanical properties of the Earth's interior by means of surface measurements of particle velocities. In recent times, the development of geodetic techniques introduced an independent measurement of the particle displacement of the Earth's surface, allowing new observations of the changes in time of the latter, and thus enabling a valuable comparative relation to seismological observations. The purpose of our study is to evaluate the temporal variations of the Earth's shallow crust in a study site located in the Italian South-Eastern Alps with the use of a seismic network managed by OGS. In our research we apply Moving-Window Cross-Spectral (MWCS) analysis to ambient-noise cross-correlations at the frequency band dominated by oceanic microseisms. This technique makes use of the seismic late arrivals (coda waves) retrieved from cross-correlation functions over multiple instants of time. The analysis of the evolution of these waveforms with respect to the acquisition time enables the estimation of relative velocity changes in the region between and around the location of the seismic stations. The constant presence of oceanic microseisms at the frequency band of study attests the convenience of using this type of ambient-noise signal for our monitoring purposes. The results produced in our analysis aim to verify the interpretations already obtained from geodetic observations about the hydrological discharge cycles of the study site.