Etna Radio Observatory
Nicolosi, home of the Parco dell 'Etna
collaborative project with OPERA2015 research - objectives and results - Final report
Rosario synthesis Catania Team member
The ERO (Etna Radio Observatory) station, detection of natural radio signals kindly hosted by the headquarters of Nicolosi of the Park of 'Etna, which is part of the radio-seismic phenomena monitoring project OPERA (Permanent Observatory Emissions RAdio-seismic), played an important role in data collection, the project carried out for a whole year, by analyzing the seismic events on a global scale, from the point of view of radio or analyzing natural phenomena, through sensors that capture and interpret their radio emissions (generated by propagation of electromagnetic waves from the source of the phenomenon).
To better understand the importance of research, totally independent and self-financed, they attach some tables and images, synthesizing according to a logic of the study, a kind of OPERA Decalogue. Table 1 represents the monitoring of the project area OPERA (including ERO), which is connected with the Richter scale indices, covers events of magnitude> 4.0. All the rest at the bottom of this index, is not taken into serious consideration (at least to occur in the vicinity), for the low percentage of wave propagation over a certain distance from the sensors, and for the 'high daily frequency, because It would be extremely difficult from an analytical point of view. Suffice it to see that the
magnitude 3.0 there are at least 130 daily events and that a magnitude 8.0 is detectable to 10,000 km away!
The image 2, shows the mathematical formula, which calculates the radio-seismic index, based on the equations of Maxwell and studies carried out by researchers Bannister and Fraser-Smith. Without going into the mathematical details, I will only indicate the magnitude of M 'event (in Richter scale) and D is the distance between the source of the phenomenon and the observer (sensor). This index is measured in decibels dB, but in the case of earthquakes, the OPERA project has added the letter "e" to indicate precisely the earthquake, so dBe, associating by convention, an earthquake of magnitude 4.0 with the epicenter 100 km away, an RI index equal to 0.
The graph 3 shows the course of 'index RI depending on the magnitude and distance.
In 2015, INGV has documented more than 15,000 seismic events, those with magnitude> 3.2 are about 279 and of these, applying the formula of 'RI, at least 46 are being studied for possible radio emissions. In Table 4, it shows how the city of Catania is present 3 times with magnitude 3,2-3,4-3,6 and index RI> 13. In the specific case it is possible that the 'seismic episode dealing with the work of the Etna volcano, especially paroxysmal phenomena. But certainly the ERO station recorded seismic episodes also 14000 km away (see episode 5,166,231 in the table).
The image 5, showing a graph which shows the recording of a geomagnetic pulsation. The ERO station, thanks to its sensors, is able to record these activities of the Earth's electromagnetic field, which thus do not have any relation to the seismic activity, but they are a real example and thus a reference, a radio-natural signal. One example is the 'incident of 16 September 2015, in which a magnificent pulse was recorded at frequencies around 1 Hz, and compared to the reception of Sogliano Station, located 750 km further north in latitude. Other radio-natural signals may be captured with the ERO station are in resonance structures Haunting (SRS), which according to studies on the subject, represent the 'existence of Alfvén waves in the ionosphere.
Together with radio-natural signals, affected by the OPERA project, the station receives processes and discriminates, even many signals generated by 'human activity, the presence of fauna and atmospheric episodes, as evidenced by' image 6. In order to highlight only the natural radio signals being studied, you must delete all the signals that have nothing to do with 'seismic activity and generate false alarms. The best strategy to determine a possible precursor signal, which has become a sort of checklist adopted by OPERA, provides that:
a) any precursor signal is received simultaneously by all stations with a similar index RI;
b) comparisons should be extended to the days before and after the event, to exclude those periodic signals that have nothing to do with the episode in analysis;
c) if they display a precursor signal, this must follow an earthquake;
d) an earthquake that is simultaneously recorded with the same magnitude-distance, should give rise to a similar precursor signal.
The image 7 shows some candidate signals as possible "precursors", recorded by the ERO in the vicinity of 'seismic episode of September 20 (marked 6096411, episode 033, 20.09.2015 22:27:58, coast Siracusa, Sicily, Md. 3.8), but the comparison with the previous days, showed similar abnormalities, revealing the signal before considered, a false precursor!
L 'image 8 shows a volcanic episode of' Etna, with the time to start and end of a paroxysm (episode 004, 01.31.2015 06:30:00, Etna volcano eruption). In this case they are placed in relation to the geophone and the antenna for the low frequencies of the ERO station, and it is evident how the seismicity pre and post event, generated by the upwelling of magmatic flow towards the summit mouths, is clearly visible on both sensors (geophone and antenna), while the moment of start and end of the paroxysm (of lava shreds emission, gas and dust with strong limited intensity and duration), is visible are on the geophone, while no track is highlighted by the electromagnetic signal coming from ' low frequency antenna (COIL-ULF).
Graph 9 shows the distribution of the episodes monitored in 2015, classified into three zones (GREEN-GREY-BLACK), depending on their intensity radiosismica in dBe.
The image 10 shows the distribution of the detection stations of the radio-natural signals, forming part of the OPERA project. The number 03 as the ERO, installed on the slopes of the 'Etna. I would say proudly representative, if we consider the total absence of stations in south-central Italian!
Antenna for ultra low frequency (ULF - COIL), and amplifier circuit.
Antenna for low frequency (VLF - IDEALLOOP H301), and amplifier circuit
Geophone for earthquakes, and amplifier circuit.