We found that:
- the maximum difference between the deepest instrument and the one at the surface is about -33 dB at 5Hz, while for the most extreme frequencies of the investigated range the noise reduction ranging from -10 to -15;
- the dependence of noise levels (in dB) with depth follows a logarithmic empirical law;
- the lower magnitude event shows the maximum difference of SNR between the deepest sensor and the one at surface of about 20 dB, in agreement with the noise amplitude level reduction range.
Seismix srl, Palermo
Department of Physics and Astronomy, Alma Mater Studiorum University of Bologna
Department of Civil, Chemical, Environmental and Materials Engineering, Alma Mater Studiorum University of Bologna
Department of Earth Sciences, University of Pisa
Edison Stoccaggio S.p.A.