GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 2.1 299 The software “Spectrum Lab” allows saving power intensity values in a restricted frequency interval. A trigger threshold is also determined for each station depending on the locale lever of noise. The pre-processing architecture is illustrated in Figure 3. To better discriminate pulses which are not produced by the power transmission lines at 50 Hz, a Bandpass filter should be enabled with a low center frequency and a chosen Bandwidth so to exclude the power transmission line influences. This process needs of a long time observation of the site noise so to consider and to exclude magnetic pulses produced by human activity. The txt files created by this process are saved every day. The system was enabled to send alarm messages after the comparison of pulse number with a threshold. Fig. 2 - Four pulses detected at Bina Observatory in the Perugia Station; pulses are characterised by small time intervals and large frequency spectrum that are depicted as vertical lines; vertical green dashed lines which repeat every minutes are the time signature of the observatory seismographic recording system. Fig. 3 - The pre-processing architecture implemented in the “Spectrum Lab” software to select magnetic pulses. Aknowledgements. The Author would like to thank DL4YHF for the versatile software. References Bleier, T.E.; Dunson, C.; Maniscalco, M.; Bryant, N.; Bambery, R.; Freund, F.; 2009: Investigation of ULF magnetic pulsations, air conductivity changes, and infra red signatures associated with the 30 October Alum Rock M5.4 earthquake. Nat. Hazards Earth Syst. Sci., 9, 585–603.