ULF Pre-Seismic Geomagnetic Anomalous Signal Related to Mw8.1 Offshore Chiapas Earthquake, Mexico on 8 September 2017

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.

Correlations between Earthquake Properties and Characteristics of Possible ULF Geomagnetic Precursor over Multiple Earthquakes

“…In theory, the amplitude of P Z/G would increase anomalously due to the direct lithospheric emission a few weeks to several days before an earthquake. This observation was reported by prior studies [14][15][16].…”

“…Moreover, seismo-EM emission is difficult to be distinguished from the much greater background natural EM field. The polarization ratio analysis (PRA) method was used in many studies where the ratio of vertical (Z) to total horizontal (G) geomagnetic field components is used as a potential precursory parameter, referred to as P Z/G parameter, e.g., [14,15]. The premise of the method is that the seismo-EM emission is assumed to be prevalent in the Z component in contrast to the magnetospheric-originating signal which dominates the G component [16].…”

Facing Missing Observations in Data—A New Approach for Estimating Strength of Earthquakes on the Pacific Coast of Southern Mexico Using Random Censoring

“…Recent research suggests that these earthquakes should not be unexpected. An entropy change of seismicity under time reversal, considered as a non-seismic precursor of earthquakes, was identified several months before the occurrence of the major earthquake [34,35]. In this study, we developed a model of extreme values with censoring data for the earthquakes on the Pacific coast of southern Mexico using a robust and solidly-based theory.…”

Possible Correlations between the ULF Geomagnetic Signature and Mw6.4 Coastal Earthquake, Albania, on 26 November 2019

“…The results carried out using ground-based geomagnetic data and ionospheric perturbations, associated with the catastrophic earthquakes Mw9.0 Tohoku, Japan on March 2011, Mw8.3 Coquimbo, Chile on September 2015 and Mw8.1Chiapas-Mexico, on September 2017 and the Vrancea seismicity, Romania, give useful information to elaborate a specific methodology able to emphasize possible inter-relations between the pre-seismic ultralow frequency (ULF) anomalous geomagnetic signature and the above-mentioned earthquakes [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ], taking into account the following three possible earthquake generation mechanisms [ 11 ]: (a) piezomagnetic effect [ 12 ]; (b) magneto-hydrodynamic effect [ 13 ]; (c) Electrokinetic effect [ 14 , 15 ]. As regards the Mw 6.4 earthquake analysis, the following previously contributions at the EGU2020 “Sharing Geosphere Online” are briefly presented further on: a multi parameters analysis of satellite and ground based data (satellite thermal anomalies, atmospheric chemical potential, radon level variation, and very high frequency (VHF) propagation in lower atmosphere) which may supply significant information before an earthquake [ 16 ]; a statistical analysis applied to identify a precursory anomaly in the total electron content [ 17 ]; observations related to the lower ionospheric turbulence variations in the last half of 2019, in broader Balkan region [ 18 ]; INFREP Radio Network revealed variations in connection with six earthquakes (Mw > 5.0) occurred in the Balkan Peninsula and Adriatic Sea on 26 and 27 November 2019 [ 19 ]; information regarding the pre-earthquake ionospheric anomalies by using the Romanian VLF/LF Infrep receivers and Gnss Global European Networks [ 20 ]; the results carried out by the satellite thermal monitoring of Balkan region by means of robust satellite technique-TIR anomalies in the framework of a multiparametric system are emphasized in [ 21 ].…”