Investigações de anomalias ionosféricas pré-terremotos

Abstract

Electromagnetic phenomena possibly associated with seismic activity have been reported in the scientific literature, including disturbances in the ionosphere and the magnetic field of the lithosphere. The purpose of this research is to investigate and identify the occurrence of ionospheric irregularities before earthquakes occur using total electron content (TEC) data obtained from Global Navigation Satellite System (GNSS) and data provided by INTERMAGNETIC (Geomagnetic Observatory Network) where magnetometers are used in soil, which allows to measure the intensity, direction, and direction of a magnetic field that is in its proximity. Earth's TEC and magnetic field anomalies have been observed several days before earthquakes, when they may be higher or lower than those obtained under normal conditions. In addition, gravity waves associated with seismic activity were also observed in TEC measurements, whose characterization is made by Wavelet (Morlet) analysis. Here are the results of the evaluation of ionospheric disturbances attributed to earthquake precursor effects of August 7, 2011, which was intensity 7 on the Richter scale, and whose epicenter occurred in Peru near the city of Pucallpa, almost on the Acre border in Brazil. The analysis of the data of the present research suggests ionospheric anomalies outside the normal daily TEC variability. The anomalous values found are ± 0.02 to 0.75 TECU out of wraps, these values have a duration of approximately 40 minutes to 8 hours, observed on day 19 until the earthquake event, suggesting a good correlation with evidence. previously reported in scientific papers on the subject, examples, in the Turkish earthquake in August 1999 with a magnitude of 7.4 on the Richter scale, where amplitude variations of up to 0.12 TECU in the TEC fluctuation intensity and duration were observed. about 1 to 5 hours out of daily variability and another example in the 2015 Nepal earthquake with a magnitude of 7.8 on the Richter scale with amplitude variations of 0.4 to 1 TECU lasting 40 minutes to 3 hours outside of normal daily variability. In the surface magnetic field data abnormal fluctuations were identified and showed correlation with the abnormal fluctuations of the observed days of the TEC, besides these observations, in the Wavelet analysis were identified possible gravity waves associated with earthquakes with periods of 8 to 15 minutes and with duration. do not exceed 50 minutes. The validation of the results for possible earthquake precursors occurs by comparing the oscillations detected by surface magnetic field magnetometers with the periods that occurred the anomalies in the VTEC envelope. The same procedure will be adopted for the oscillations detected by individual satellites during the periods. VTEC envelope anomalies occurred and were evaluated by Wavelet analysis.