Multi-scale attenuative imaging of the Collalto UGS area and the Montello thrust system (eastern Southern Alps, Italy)

Seismic attenuation tomography is a valuable geophysical method for imaging complex geological assessments at local and regional scales. It effectively detects melt, fractures, and strain conditions in rocks, and its reliability has been confirmed through laboratory experiments.

This study focuses on locating the Collalto underground gas storage (UGS) in the eastern Southern Alps of Northern Italy through seismic attenuation tomography. It represents the first multiscale attenuation imaging of the Montello thrust, which belongs to the segment of the Alpine boundary thrust covering about 100 km from Vicenza to Pordenone. The region faces medium to high seismic hazards, monitored by a local seismic network managed by the National Institute of Oceanography and Applied Geophysics in Trieste.

Using data from this network and the Murat code, we analyzed scattering, absorption, and total attenuation, interpreting results alongside geological-structural data. Our models confirm the principal attitude of the Montello thrust system, also highlighting minor faults that distribute deformation and seismic activity.

At a local scale, the absorption model highlights the methane-rich volume (Collalto UGS) as notably attenuative, indicating the method's effectiveness in detecting fluids. It also reveals deeper attenuative patches that anti-correlate with seismicity, suggesting a deeper layer of fluids likely influencing tectonic behavior.

These results open the path for further interdisciplinary research to develop comprehensive seismotectonic models integrating seismic activity with rock properties and deformation patterns.