Worldwide Statistical Correlation of Eight Years of <i>Swarm</i> Satellite Data with M5.5+ Earthquakes: New Hints about the Preseismic Phenomena from Space
oleh: Dedalo Marchetti, Angelo De Santis, Saioa A. Campuzano, Kaiguang Zhu, Maurizio Soldani, Serena D’Arcangelo, Martina Orlando, Ting Wang, Gianfranco Cianchini, Domenico Di Mauro, Alessandro Ippolito, Adriano Nardi, Dario Sabbagh, Wenqi Chen, Xiaodan He, Xuhui Shen, Jiami Wen, Donghua Zhang, Hanshuo Zhang, Yiqun Zhang, Zhima Zeren
| Format: | Article |
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| Diterbitkan: | MDPI AG 2022-06-01 |
Deskripsi
Nowadays, the possibility that medium-large earthquakes could produce some electromagnetic ionospheric disturbances during their preparatory phase is controversial in the scientific community. Some previous works using satellite data from DEMETER, <i>Swarm</i> and, recently, CSES provided several pieces of evidence supporting the existence of such precursory phenomena in terms of single case studies and statical analyses. In this work, we applied a Worldwide Statistical Correlation approach to <b>M5.5+ shallow earthquakes</b> using the first <b>8 years of <i>Swarm</i></b> (i.e., from November 2013 to November 2021) <b>magnetic field and electron density signals</b> in order to improve the significance of previous statistical studies and provide some new results on how earthquake features could influence ionospheric electromagnetic disturbances. We implemented new methodologies based on the hypothesis that the anticipation time of anomalies of larger earthquakes is usually longer than that of anomalies of smaller magnitude. We also considered the <b>signal’s frequency</b> to introduce a new identification criterion for the anomalies. We find that taking into account the frequency can improve the statistical significance (up to 25% for magnetic data and up to 100% for electron density). Furthermore, we noted that the <b>frequency</b> of the <i>Swarm</i> <b>magnetic field signal</b> of possible precursor anomalies seems to slightly <b>increase as the earthquake is approaching</b>. Finally, we checked a possible relationship between the frequency of the detected anomalies and earthquake features. The earthquake focal mechanism seems to have a low or null influence on the frequency of the detected anomalies, while the epicenter location appears to play an important role. In fact, <b>land</b> earthquakes are more likely to be preceded by <b>slower</b> (lower frequency) magnetic field signals, whereas <b>sea</b> seismic events show a higher probability of being preceded by <b>faster</b> (higher frequency) magnetic field signals.