Theory of electrokinetic‐magnetic anomalies in a faulted half‐space

Fitterman, David V.

doi:10.1029/jb084ib11p06031

Cited by 139 publications

(83 citation statements)

References 18 publications

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“…However, three possible generation mechanisms have been proposed for ULF electromagnetic anomalies, which are discussed in Molchanov and Hayakawa (2008). The possible mechanisms to generate such ULF variations are electrokinetic effect (Mizutani et al, 1976;Fittermen, 1978Fittermen, , 1979Fittermen, , 1981Ishido and Mizutani, 1981;Dobrovolsky et al, 1981;Fenoglio, 1991), microfracturing Hayakawa, 1995, 1998), and conductivity change (Scholz et al, 1973;Draganov et al, 1991;Surkov and Pulipenko, 1999). Our results in Fig.…”

Section: Discussionmentioning

confidence: 99%

Ultra low frequency (ULF) electromagnetic anomalies associated with large earthquakes in Java Island, Indonesia by using wavelet transform and detrended fluctuation analysis

Febriani

Han

Yoshino

et al. 2014

Nat. Hazards Earth Syst. Sci.

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Abstract. Indonesia is one of the most seismically active regions in the world and mitigation of seismic hazard is important. It is reported that Ultra low frequency (ULF) geomagnetic anomalies are one of the most convincing phenomena preceding large earthquakes (EQs). In this paper we have analyzed geomagnetic data at Pelabuhan Ratu (PLR) (7.01 • S, 106.56 • E), Sukabumi, West Java, Indonesia, from 1 September 2008 to 31 October 2010. There are twelve moderate-large EQs (M ≥ 5) within 160 km from the station during the analyzed period. The largest one is the M = 7.5 EQ (depth = 57 km, epicentral distance = 135 km, 2 September 2009) based on EQ catalog of Indonesian Meteorological, Climatological and Geophysical Agency (BMKG). To investigate the ULF geomagnetic anomalous variations preceding all the EQs, spectral density ratio at the frequency range of 0.01 ± 0.003 Hz based on wavelet transform (WT) and detrended fluctuation analysis (DFA) have been carried out. The spectral density ratio results show the enhancements a few weeks before the largest EQ. The enhancement persists about one week and reaches a maximum on 16 August 2009. At the same time, the result of the DFA presents the decrease of α value. For other EQs, there are no clear increases of the spectral density ratio with simultaneous decrease of α value. When these phenomena occur, the value of Dst index shows that there are no peculiar global geomagnetic activities at the low latitude region. The above results are suggestive of the relation between the detected anomalies and the largest EQ.

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Section: Discussionmentioning

confidence: 99%

Ultra low frequency (ULF) electromagnetic anomalies associated with large earthquakes in Java Island, Indonesia by using wavelet transform and detrended fluctuation analysis

Febriani

Han

Yoshino

et al. 2014

Nat. Hazards Earth Syst. Sci.

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“…Electrokinetically generated electric and magnetic fields [Mizutani and Ishido, 1976;Fitterman, 1978Fitterman, , 1979 [Loeb, 1958]. Charge generation by rapid fluid disruption is thus a well-known phenomenon and is not, of much concern if this charge is generated in a conducting environment, since it will quickly decay [Locknet et al, 1983].…”

Section: Physical Backgroundmentioning

confidence: 99%

Rapid fluid disruption: A source for self‐potential anomalies on volcanoes

Johnston¹,

Byerlee²,

Lockner³

2001

J. Geophys. Res.

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Abstract. Self-potential (SP) anomalies observed above suspected magma reservoirs, dikes, etc., on various volcanoes (Kilauea, Hawaii; Mount Unzen, Japan; Piton de la Fournaise, Reunion Island, Miyake Jima, Japan) result from transient surface electric fields of tens of millivolts per kilometer and generally have a positive polarity. These SP anomalies are usually attributed to electrokinetic effects where properties controlling this process are poorly constrained. We propose an alternate explanation that contributions to electric fields of correct polarity should be expected from charge generation by fluid vaporization/disruption. As liquids are vaporized or removed as droplets by gas transport away from hot dike intrusions, both charge generation and local increase in electrical resistivity by removal of fluids should occur. We report laboratory observations of electric fields in hot rock samples generated by pulses of fluid (water) through the rock at atmospheric pressure. These indicate the relative amplitudes of rapid fluid disruption (RFD) potentials and electrokinetic potentials to be dramatically different and the signals are opposite in sign. Above vaporization temperatures, RFD effects of positive sign in the direction of gas flow dominate, whereas below these temperatures, effects of negative sign dominate. This suggests that the primary contribution to observed self-potential anomalies arises from gas-related charge transport processes at temperatures high enough to produce vigorous boiling and vapor transport. At lower temperatures, the primary contribution is from electrokinetic effects modulated perhaps by changing electrical resistivity and RFD effects from high-pressure but low-temperature COe and SOe gas flow ripping water molecules from saturated crustal rocks. If charge generation is continuous, as could well occur above a newly eraplaced dike, positive static potentials will be set up that could be sustained for many years, and the simplest method for identii•ying these hot, active regions would be to identi•y the SP anomalies they generate.

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“…The volcanomagnetic variations, whether being of electrofiltration type (MITZUTANI et al,1976;FITTERMAN, 1978FITTERMAN, , 1979 or of diffusion type (ZLOTNICKI et al, submitted), are both related to magnetic variations which are induced by electric current flowing in geological structures. The electrofiltration type variations are most often caused by a ion-carrying fluid flowing along liquid-solid interfaces under the action of a pore pressure gradient.…”

Section: Transient Variationsmentioning

confidence: 99%