We used a broadband (BB) seismic station at surface and a vertical array composed by 6-short period 3-components seismometers installed at depth ranging between 35 to 285 m in borehole at the same location of the BB sensor.
We found that:
- an evident noise reduction with depth for frequencies from 1 to 10 Hz;
- for some frequencies, the noise level is below the NHNM only at depth larger than 85 m;
- most of the noise reduction occurs between 0 and 35 m;
- the decrease of noise level (dB) as function of depth follows a logarithmic trend
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.