Review of magnetic and electric field effects near active faults and volcanoes in the U.S.A.

Johnston, M. J. S.

doi:10.1016/0031-9201(89)90213-6

Cited by 61 publications

(32 citation statements)

References 46 publications

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“…Our analysis is based on differential measurements between the two permanent observatories of L'Aquila and Duronia in order to minimize the contamination from multiple sources, such as the local background noise and the magnetic field of external origin. Many experimental and theoretical studies on the electromagnetic phenomena associated with earthquakes in the frequency range from ULF to HF have been reported, see Varotsos et al, 1984a, b, Bernardi et al, 1991Fenoglio et al, 1995;Fraser-Smith et al, 1990, 1993Gershenzon et al, 1989;Gokhberg et al 1982;Hayakawa et al, 1996;Johnston et al, 1987Johnston et al, , 1989Johnston et al, , 1994Johnston et al, , 1997Merzer et al, 1997;Molchanov et al, 1992Molchanov et al, , 1995Nagano et al, 1975;Parrot et al, 1989;Park et al, 1991Park et al, , 1993Palangio et al, 2007Palangio et al, , 2008. These studies focus on different aspects including variations in quasi-static electric and magnetic fields, telluric potentials, ULF magnetic fields, alternating electric fields in the ULF, ELF and VLF bands, and variations in the ground resistivity.…”

Section: Introductionmentioning

confidence: 99%

Non-inductive components of electromagnetic signals associated with L'Aquila earthquake sequences estimated by means of inter-station impulse response functions

Lorenzo

Palangio

Santarato

et al. 2011

Nat. Hazards Earth Syst. Sci.

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Abstract. On 6 April 2009 at 01:32:39 UT a strong earthquake occurred west of L'Aquila at the very shallow depth of 9 km. The main shock local magnitude was M l = 5.8 (Mw = 6.3). Several powerful aftershocks occurred the following days. The epicentre of the main shock occurred 6 km away from the Geomagnetic Observatory of L'Aquila, on a fault 15 km long having a NW-SE strike, about 140 • , and a SW dip of about 42 • . For this reason, L'Aquila seismic events offered very favourable conditions to detect possible electromagnetic emissions related to the earthquake. The data used in this work come from the permanent geomagnetic Observatories of L'Aquila and Duronia. Here the results concerning the analysis of the residual magnetic field estimated by means of the inter-station impulse response functions in the frequency band from 0.3 Hz to 3 Hz are shown.

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Section: Introductionmentioning

confidence: 99%

Non-inductive components of electromagnetic signals associated with L'Aquila earthquake sequences estimated by means of inter-station impulse response functions

Lorenzo

Palangio

Santarato

et al. 2011

Nat. Hazards Earth Syst. Sci.

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“…Over the past decades, there have been many observation reports of electromagnetic disturbances in the frequency range of 10 -3 to 10 8 Hz before large earthquakes (e.g., Kalashnikov 1954;Johnston 1989;Parrot 1990;Hayakawa and Molchanov 2008). Among them, disturbance signals at the ELF range below 10 Hz were featured in several studies.…”

Section: Introductionmentioning

confidence: 99%

The Characteristics of Magnetic Signals Observed at Lulin ELF Station and Their Association with Earthquakes in Taiwan

Ho¹,

Wang²,

Chen³

et al. 2013

Terr. Atmos. Ocean. Sci.

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Electromagnetic wave data from years 2009 -2010 which were recorded by the extremely-low-frequency (ELF) station at Lulin Observatory in Taiwan (120.87°E, 23.46°N; 2862 m) are analyzed to explore the wave properties and their association with seismic and geomagnetic activities. Specifically, the power spectra, the ellipticity and the orientation of the below-10-Hz wave signals are studied. The correlation coefficients of these ELF signals and geomagnetic activity indices Dst and Kp are within -0.2 to 0.2, indicating geomagnetic activities are not likely sources for these emissions. In the frequency versus time (f-t) spectrograms, a few events exhibit a frequency shift between 4 and 6 Hz and the possible association with seismic activities of magnitudes (M) larger than 4 in the vicinity of Taiwan are examined. The subset of earthquakes in Taiwan with M/r 2 (r is the epicenter distance in kilometer from the Lulin station) of greater than 6 × 10 -4 , a total number of 50, show a higher association with ELF wave events showing a frequency down-shift within 7 days prior to the earthquakes and a frequency bounce-back within 7 days after the earthquakes. The epicenters of these earthquakes are all within a distance of 100 km from the Lulin station and with a depth of 50 km, suggesting that the detected ELF frequency-shift wave events maybe are pre-earthquake electromagnetic signals.

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“…Since fluctuations are present even when no volcanic activity is apparently affecting the signal (e.g. Johnston, 1989;Zlotnicki et al, 2000;Del Negro et al, 2004) it is evident that external sources are responsible for these variations. Hence, it is necessary to correct this component in order to identify significant geophysical signals.…”

Section: Introductionmentioning

confidence: 99%

Denoising gravity and geomagnetic signals from Etna volcano (Italy) using multivariate methods

Negro

Greco

Napoli

et al. 2008

Nonlin. Processes Geophys.

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Abstract.Multivariate methods were applied to denoise the gravity and geomagnetic signals continuously recorded by the permanent monitoring networks on the Etna volcano. Gravity and geomagnetic signals observed in volcanic areas are severely influenced by meteorological variables (i.e. pressure, temperature and humidity), whose disturbances can make the detection of volcanic source effects more difficult. For volcano monitoring it is necessary, therefore, to reduce the effects of these perturbations. To date filtering noise is a very complex problem since the spectrum of each noise component has wide intervals of superposition and, some times, traditional filtering techniques provide unsatisfactory results. We propose the application of two different approaches, the adaptive neuro-fuzzy inference system (ANFIS) and the Independent Component Analysis (ICA) to remove noise effects from gravity and geomagnetic time series. Results suggest a good efficiency of the two proposed approaches since they are capable of finding and effectively representing the underlying factors or sources, and allow local features of the signal to be detected.

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Review of magnetic and electric field effects near active faults and volcanoes in the U.S.A.

Cited by 61 publications

References 46 publications

Non-inductive components of electromagnetic signals associated with L'Aquila earthquake sequences estimated by means of inter-station impulse response functions

Non-inductive components of electromagnetic signals associated with L'Aquila earthquake sequences estimated by means of inter-station impulse response functions

The Characteristics of Magnetic Signals Observed at Lulin ELF Station and Their Association with Earthquakes in Taiwan

Denoising gravity and geomagnetic signals from Etna volcano (Italy) using multivariate methods

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