On effective ULF frequency ranges for geomagnetic earthquake precursor

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

doi:10.1088/1742-6596/1152/1/012033

Cited by 10 publications

(6 citation statements)

References 24 publications

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“…This step was to minimize human-made noise during the day. Frequency ranges, ∆f in prior studies were arbitrarily chosen [33], hence nine ranges were tested to determine the most effective one for each earthquake: ∆f = 0.01-0.02, 0.02-0.03, . .…”

Section: Precusor Detectionmentioning

confidence: 99%

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

et al. 2021

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In this study, we improved and adapted existing signal processing methods on vast geomagnetic field data to investigate the correlations between various earthquake properties and characteristics of possible geomagnetic precursors. The data from 10 magnetometer stations were utilized to detect precursory ultra-low frequency emission and estimate the source direction for 34 earthquakes occurring between the year 2007–2016 in Southeast Asia, East Asia, and South America regions. As a result, possible precursors of 20 earthquakes were identified (58.82% detection rate). Weak correlations were obtained when all precursors were considered. However, statistically significant and strong linear correlations (r ≥ 0.60, p < 0.05) were found when the precursors from two closely located stations in Japan (Onagawa (ONW) and Tohno (TNO)) were exclusively investigated. For these stations, it was found that the lead time of the precursor is strongly (or very strongly) correlated with the earthquake magnitude, the local seismicity index, and the hypocentral depth. In addition, the error percentage of the estimated direction showed a strong correlation with the hypocentral depth. It is concluded that, when the study area is restricted to a specific location, the earthquake properties are more likely to have correlations with several characteristics of the possible precursors.

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Section: Precusor Detectionmentioning

confidence: 99%

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

et al. 2021

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“…If anything else, this short analysis demonstrates that the choice of the frequency of interest is not a trivial one. Yusof et al (2019) find no apparent correlation between effective ULF frequency ranges with magnitudes, depths or epicentral distances, without any better solution, we advise that future studies do not restrict themselves to a narrow frequency band but instead explore the frequency space in a systematic way. We also think that a better physical understanding of the alleged pre-earthquake ULF anomalies is needed to narrow the frequency band of interest.…”

Section: Sensitivity To Frequencymentioning

confidence: 88%

“…The central frequency of 0.02 Hz is of special interest, as it was identifed by Yusof et al (2019) as being “optimal for earthquake prediction purpose.” Yusof et al (2019) perform a bibliographical analysis in which they plot the percentage of success achieved in previous studies against the effective ULF frequency range in use, using 0.01‐Hz increments, exploring frequencies ranging from 0.01 to 1.5 Hz. They conclude that both the 0.02–0.03 Hz (or 0.04 Hz as mentioned in their introduction) and the 0.06‐Hz bands are especially pertinent.…”

Section: Sensitivity Studymentioning

confidence: 99%

“…As recently pinpointed by Yusof et al (2019), restricting the search for pre‐earthquake EM signals to a somewhat narrow frequency band is rather arbitrary. One may indeed wonder how changing the central frequency of the “band‐pass” filtering applied prior to daily energy computation would affect the 5‐day stacked plots shown in section 2.3.3.…”

Section: Sensitivity Studymentioning

confidence: 99%

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Statistical Analysis of Pre‐earthquake Electromagnetic Anomalies in the ULF Range

et al. 2020

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Assessing the statistical significance of electromagnetic anomalies in the ultralow frequency (ULF) range observed prior to earthquakes is a necessary step toward determining whether these perturbations constitute actual earthquake precursors. A statistical epoch analysis (SEA) was recently performed by Han et al. (2014, https://doi.org/10.1002/2014JA019789) to analyze earthquakes happening between 2001 and 2010 near the geomagnetic observatory of Kakioka, Japan; the authors found a significant number of anomalies 6 to 15 days prior to the earthquake day within 100 km from Kakioka, while no significant pre-earthquake activity was observed for the farther region 100 to 216 km from the observatory. In this current paper, we describe the application of our independent software implementation of their method. Despite using a different outlier rejection scheme, we manage to approximate their results. Upon validation of our program, we conduct multiple sensitivity studies. First, we explore how different outlier rejection schemes impact the results. We then restrict the analysis to only mantle earthquakes, highlighting a marginally significant number of anomalies prior to the earthquake day. Next, we test a higher band-pass filter than the one initially used but find no anomalous pre-earthquake activity in this higher-frequency band. We then use a different catalog to establish the list of qualifying "earthquake days" which also leads the anomalous pre-earthquake episode to vanish, thus raising concerns about the robustness of the results. Finally, we apply the SEA to another time window, ranging from 2013 to 2018: No significant pre-earthquake episode can be observed for this interval. We conclude our study by providing guidelines for upcoming work.

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“…Several studies have been conducted to monitor the activity of the earth's crust linked to electromagnetic anomalies within the limit of ULF (f<10 Hz) in terms of earthquake precursors. Previous studies have successfully shown that the ULF range within 0.01-0.1 Hz gave the best results for detecting electromagnetic anomalies in terms of earthquake precursors [5,6,7]. However, the ULF emission that can be assigned as electromagnetic anomalies has sometimes been problematic because not only is the intensity very weak (around 1nT) but it is usually difficult to understand as well due to the intense natural background of the geomagnetic field [8].…”

Section: Introductionmentioning

confidence: 99%

Geomagnetic anomaly associated with Fukushima earthquake on February 13^th, 2021

et al. 2021

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In this study, we performed research on electromagnetic anomalies related to earthquakes as early signs (precursors) that occurred in Fukushima, Japan on February 13th, 2021. The research focused on the utilization of geomagnetic field data which was derived from the Kakioka (KAK), Kanoya (KNY), and Memambetsu (MMB) observatories, particularly in the ultra-low frequency (ULF) to detect earthquake precursors. The method of electromagnetic data processing was conducted by applying a polarization ratio. In addition, we improved the methodology by splitting the ULF data (which ranged from 0.01-0.1 Hz) into 9 central frequencies and picking up the highest value from each central frequency to get the polarization ratio. The anomaly of magnetic polarization was identified 2-3 weeks before the mainshock in a narrowband frequency in the range of 0.04-0.05 Hz.

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On effective ULF frequency ranges for geomagnetic earthquake precursor

Cited by 10 publications

References 24 publications

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

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

Statistical Analysis of Pre‐earthquake Electromagnetic Anomalies in the ULF Range

Geomagnetic anomaly associated with Fukushima earthquake on February 13^th, 2021

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On effective ULF frequency ranges for geomagnetic earthquake precursor

Cited by 10 publications

References 24 publications

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

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

Statistical Analysis of Pre‐earthquake Electromagnetic Anomalies in the ULF Range

Geomagnetic anomaly associated with Fukushima earthquake on February 13th, 2021

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Geomagnetic anomaly associated with Fukushima earthquake on February 13^th, 2021