GNGTS 2017 - 36° Convegno Nazionale

318 GNGTS 2017 S essione 2.1 Fig. 2. Pulse rates increased about four hours before the quakes. Horizontal lines denote omnipresent magnetic oscillations produced by the power distribution line. Another shape appeared during the same period, and were like spots which covered the 20 - 40 Hz spectrum and were several minutes in duration, appearing among pulses, see Fig. 2. The overall average pulse number was about 10. There was no evidence of daily pulse number increases around the Amatrice main event on August 24, 2016. Unfortunately, data are not available for the week prior this event, see Fig. 3. The daily number of pulses on August 24, 2016, was lower than the average value. Being so, no magnetic anomalies were recorded around the Amatrice event. Daily numbers of magnetic pulses increased suddenly on October 26, around moderate shocks occurring 20 km north of Amatrice. The number of magnetic pulses was equal to 30 on October 26, 45 on October 27, around 90 on October 28, returned to 30 on October 29 and increased to 60 on October 30, when a strong earthquake struck Norcia. Daily numbers of pulses continued to increase up until November 3, reaching a peak of 90 counts. On June 2017, a triaxial accelerometer was installed at the Norcia Station; on board this was a triaxial magnetometer typically used to realise a compass. The board is connected to a PC with a USB cable, which supplies the circuit and receives data in ascii format using a Phyton main software, which creates a daily text file with all the parameters including the time stamp. The firmware of the processor is able to read data from the accelerometer at the speed of 100 Hz while it reads the magnetometer at a maximum speed of 80 Hz. On September 3, 2017, small variations in the Y-axis were recorded just two days before a shock of 3.7 occurring in Campotosto. To date, no evidence of significant triaxial magnetic variations have been recorded before, during or after any earthquakes. Acknowledgements Authors would like to thank Tommasi Cecci for realising the loops for the Avigliano Umbro and Norcia Stations. Additionally, authors would like to express his thanks to Marco Eleuteri for realising the Narni Station loop. Finally, authors would like to thank Adriano Nardi and Ernesto Tiberi for their contribution to installing the Norcia Station. References Fidani C.; 2011: The Central Italy Electromagnetic Network and the 2009 L’Aquila earthquake: observed electric activity. Geoscience, 1, 3-25. Fidani C. and Martinelli G.; 2015: A possible explanation for electric perturbations recorded by the Italian CIEN stations before the 2012 Emilia earthquakes, Bollettino di Geofisica Teorica ed Applicata, 56, 2, 211-226. Fidani C. and Marcelli D.; 2017: Ten Years of the Central Italy Electromagnetic Network (CIEN) Continuous Monitoring, Open Journal of Earthquake Research, 6, 73-88. Orsini M.; 2011: Electromagnetic anomalies recorded before the earthquake of L’Aquila on April 6, 2009. Bollettino di Geofisica Teorica e Applicata, 52, 1, 123-130. Fig. 3 - Distribution of daily magnetic pulse numbers around the four strong quakes striking central Italy. An unexpected increase in the number of daily magnetic pulses occurred on October 26, 2016, no increases were observed around the Amatrice earthquake. The turquoise colored areas indicate unavailable data.