Abstract
In the last decade, the real time ground–based geomagnetic observations realized in correlation with the Vrancea seismicity in Romania, together with supplementary studies related to some earthquakes (Mw9.0 Tohoku, Japan on 11 March 2011 and Mw8.3 Coquimbo, Chile on 16 September 2015), enlarged our knowledge about the relationship between the pre-seismic anomalous phenomena and the final stage of the earthquake nucleation. To identify possible ultra-low-frequency (ULF) geomagnetic signals prior to the onset of an Mw8.1 earthquake, we retroactively analyzed the data collected on the interval 1 August–16 September 2017 at the Geomagnetic Observatories in Teoloyucan (TEO), Mexico and Tucson (TUC) USA, with the last taken as a reference. Daily mean distributions of the polarization parameter BPOL (geomagnetic polarization parameter) and standard deviation are obtained for both observatories using a fast Fourier transform (FFT) band-pass filtering in the ULF range (0.001–0.083 Hz). Further on, we investigated the singularity of the pre-seismic signal associated with an Mw8.1 earthquake and applied a statistical analysis based on a standardized random variable equation; results are presented as BPOL* time series on the interval 1–26 September. Finally, the hourly mean distribution, obtained as difference BPOL (TUC-TEO) on the interval 7–9 September emphasizes an anomalous signal with five hours before the onset of the Mw8.1 earthquake.
Highlights
Electromagnetic phenomena related to the seismic events have been extensively analyzed by different scientific groups, and a variety of the short-term pre-seismic anomalous signals covering a wide range of frequencies from DC to very high frequency (VHF) using ground-based and satellite observation techniques are detected [1]
3.1–3.3), we present the mean distributions of the geomagnetic parameters carried daily mean mean distributions distributions of of the the geomagnetic geomagnetic parameters parameters BPOL, BPOL, BPOL*
In order to emphasize possible interrelation between the pre-seismic geomagnetic signature and the Mw8.1 Chiapas earthquake, in this paper we have investigated the ULF geomagnetic data recorded at the Teoloyucan and Tucson geomagnetic observatories on the interval August–September 2017
Summary
Electromagnetic phenomena related to the seismic events have been extensively analyzed by different scientific groups, and a variety of the short-term pre-seismic anomalous signals covering a wide range of frequencies from DC to very high frequency (VHF) using ground-based and satellite observation techniques are detected [1]. Theinstrumentation, ULF geomagnetic pre-seismic type from of the electromagnetic precursors range, method of signals associated seven major earthquakes generated in Mexicoand during the interval of 1999–2001 detection with with precursory time, effective distance from epicenter, references are analyzed in detail [30]. Geomagnetic data havegenerated an important role in the pre-seismic investigation This means more accurate collected from both ground-based and satellites observatories have an important role in the knowledge about the origin of the internal and external parts of the geomagnetic sourcesprecould signal separation investigation. In this study, we used the data collected from the geomagnetic the transient local anomalies associated with Mw8.1 earthquake by the internal and external parts observatories in Teoloyucan, Mexico, and Tucson, USA. Band-passfiltering filtering(red (redline) line) applied applied on polarization parameter) time series (blue line) for a time windows of samples recorded polarization parameter) time series (blue line) for a time windows of 1024 samples recorded on 1on
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