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Ionospheric anomalies detection using autoregressive integrated moving average (ARIMA) model as an earthquake precursor

Saqib Mohd, Şentürk Erman, Sahu Sanjeev Anand, Adil Muhammad Arqim

Acta Geophysica

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2021

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Vol. 69, no. 4

1493--1507

EN

The ARIMA method, time series analysis technique, was proposed to perform short-term ionospheric Total Electron Content (TEC) forecast and to detect TEC anomalies. The success of the method was tested in two major earthquakes that occurred in India (M 7.7 Bhuj EQ, on Jan 26, 2001) and Turkey (M 7.1 Van EQ, on Oct 23, 2011). For ARIMA analysis, we have taken 18 and 29 days of TEC data with a 2-h temporal resolution and train the model with an accuracy of 5.1 and 2.7–2.9 TECU for India and Turkey EQs, respectively. After training the model and optimizing hyper model parameters, we applied on 8 and 9 days’ time-window to observe anomalies. In Bhuj EQ, the negative anomalies are recorded on Jan 19 and 22, 2001. Similarly, positive anomalies are recorded on Jan 23, 24, and 25, 2001. In Van EQ, we recorded a strong positive anomaly on Oct 21, 2011, and in the consecutive days before the earthquake, some weak negative anomalies have also observed. The results showed that ARIMA has an adequate short-term performance of the ionospheric TEC prediction and anomaly detection of the TEC time series.

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Assessment of signal processing methods for geomagnetic precursor of the 2012 M6.9 Visayas, Philippines earthquake

Yusof Khairul Adib, Hamid Nurul Shazana Abdul, Abdullah Mardina, Ahadi Suaidi, Yoshikawa Akimasa

Acta Geophysica

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2019

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Vol. 67, no. 5

1297--1306

EN

This study assessed two signal processing methods on geomagnetic data to detect precursory signals appearing before the M6.9 Visayas, Philippines earthquake on 6 February 2012. It aimed to compare the polarization ratio analysis method with the diurnal variation ratio method in terms of reliability and efectiveness. The geomagnetic data were obtained from the MAGDAS magnetometer network for Cebu (CEB) and Legazpi (LGZ) stations which served as the primary and remote stations, respectively. The polarization ratio analysis method was performed on the primary station data to obtain power spectral density in an ultra-low-frequency range before fnding the ratio of vertical to total horizontal component. Meanwhile, the diurnal variation ratio method was used to calculate the diference between the daily maximum and minimum values. Then, the ratio of the daily diferences of the primary station to the remote station for each individual component was calculated. The disturbance storm time index which describes global geomagnetic activity originating from the Sun was utilized to verify that any observed geomagnetic fuctuations were not caused by solar-terrestrial efect. A precursory anomaly was found using the polarization ratio analysis method which appeared 2 weeks before the earthquake. It is concluded that this method might be efective and reliable in detecting geomagnetic anomalies preceding upcoming earthquakes. In contrast, although the diurnal variation ratio method did show perceivable fuctuations, the running averages were not statistically significant to be considered a precursor. The discrepancy between the analytical results of the two methods may be attributed to the detectability of the earthquake being studied which had a relatively low magnitude. Hence, future studies which utilize more earthquake events need to be conducted to reach a definitive conclusion.

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A statistical analysis of seismo‑ionospheric TEC anomalies before 63 Mw ≥ 5.0 earthquakes in Turkey during 2003–2016

Şentürk E., Çepni M. S.

Acta Geophysica

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2018

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Vol. 66, no. 6

1495--1507

EN

In this study, pre-seismic and post-seismic total electron content (TEC) anomalies of 63 Mw ≥ 5.0 earthquakes in Turkey (36°–42°N, 26°–45°E) were statistically investigated. The largest earthquake that occurred in Turkey during 2003–2016 is the Mw 7.1 Van earthquake on October 23, 2011. The TEC data of epicenters is obtained from CODE-GIM using a simple 4-point bivariate interpolation. The anomalies of TEC variations were determined by using a quartile-based running median process. In order to validate GIM results, we used the GPS-TEC data of available four IGS stations within the size of the Van earthquake preparation area. The anomalies that are detected by GIM and GPS-TEC show a similar pattern. Accordingly, the results obtained with CODE-GIM are reliable. The statistical results show that there are not prominent earthquake precursors for Mw ≤ 6.0 earthquakes in Turkey.

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Cross-correlation earthquake precursors in the hydrogeochemical and geoacoustic signals for the Kamchatka peninsula

Ryabinin G., Gavrilov V., Polyakov Y., Timashev S.

Acta Geophysica

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2012

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Vol. 60, no. 3

874-893

EN

We propose a new type of earthquake precursor based on the analysis of correlation dynamics between geophysical signals of different nature. The precursor is found using a two-parameter cross-correlation function introduced within the framework of flicker-noise spectroscopy, a general statistical physics approach to the analysis of time series. We consider an example of cross-correlation analysis for water salinity time series, an integral characteristic of the chemical composition of groundwater, and geoacoustic emissions recorded at the G-1 borehole on the Kamchatka peninsula in the time frame from 2001 to 2003, which is characterized by a sequence of three groups of significant seismic events. We found that cross-correlation precursors took place 27, 31, and 35 days ahead of the strongest earthquakes for each group of seismic events, respectively. At the same time, precursory anomalies in the signals themselves were observed only in the geoacoustic emissions for one group of earthquakes.