Comment on “Natural magnetic disturbance fields, not precursors, preceding the Loma Prieta earthquake” by Wallace H. Campbell

Fraser–Smith, A. C.; McGill, Paul; Bernardi, Andrea

doi:10.1029/2010ja016379

Cited by 10 publications

(15 citation statements)

References 25 publications

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“…Fraser‐Smith et al . [] do not concur with the criticism of Campbell [] who argues that the magnetic changes preceding the Loma‐Prieta earthquake were natural disturbances coincidental to the geomagnetic solar‐terrestrial disturbance field. However, we agree with Fraser‐Smith et al .…”

Section: Many Papers and Many Ulf Precursorsmentioning

confidence: 74%

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Are there new findings in the search for ULF magnetic precursors to earthquakes?

Masci

Thomas

2015

JGR Space Physics

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Moore (1964) in a letter published in Nature reported disturbances in geomagnetic field data prior to the 27 March 1964 Alaska earthquake. After the publication of this report, many papers have shown magnetic changes preceding earthquakes. However, a causal relationship between preearthquake magnetic changes and impending earthquakes has never been demonstrated. As a consequence, after 50 years, magnetic disturbances in the geomagnetic field are still candidate precursory phenomena. Some researchers consider the investigation of ultra low frequency (ULF: 0.001–10 Hz) magnetic data the correct approach for identifying precursory signatures of earthquakes. Other researchers, instead, have recently reviewed many published ULF magnetic changes that preceded earthquakes and have shown that these are not actual precursors. The recent studies by Currie and Waters (2014) and Han et al. (2014) aim to provide relevant new findings in the search for ULF magnetic precursory signals. However, in order to contribute to science, alleged precursors must be shown to be valid and reproducible by objective testing. Here we will briefly discuss the state of the art in the search for ULF magnetic precursors, paying special attention to the recent findings of Currie and Waters (2014) and Han et al. (2014). We do not see in these two reports significant evidence that may support the observation of precursory signatures of earthquakes in ULF magnetic records.

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Section: Many Papers and Many Ulf Precursorsmentioning

confidence: 74%

“…However, we agree with Fraser‐Smith et al . [] that, according to the normal scientific process, further independent evidence is required before the magnetic field fluctuations prior to the Loma‐Prieta earthquake may be considered as a real precursor.…”

Section: Many Papers and Many Ulf Precursorsmentioning

confidence: 99%

Are there new findings in the search for ULF magnetic precursors to earthquakes?

Masci

Thomas

2015

JGR Space Physics

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“…For example, one of the most frequently cited magnetic anomalies preceded the Loma Prieta earthquake (Fraser-Smith et al, 1990). Some authors dismiss this as normal geomagnetic activity enhanced by operator or amplifier malfunction (Campbell, 2009;Thomas et al, 2009), while counterarguments (Fraser-Smith et al, 2011) point out that continuous calibration tests should preclude this as a possibility, that the precursor lacks the diurnal behavior of typical geomagnetic activity, and that amplifier malfunction would not preferentially amplify low-frequency signals. (FraserSmith et al, 2011) states that ".…”

Section: Introductionmentioning

confidence: 99%

Pre-earthquake magnetic pulses

Scoville

Heraud

Freund

2015

Nat. Hazards Earth Syst. Sci.

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Abstract.A semiconductor model of rocks is shown to describe unipolar magnetic pulses, a phenomenon that has been observed prior to earthquakes. These pulses are suspected to be generated deep in the Earth's crust, in and around the hypocentral volume, days or even weeks before earthquakes. Their extremely long wavelength allows them to pass through kilometers of rock. Interestingly, when the sources of these pulses are triangulated, the locations coincide with the epicenters of future earthquakes. We couple a drift-diffusion semiconductor model to a magnetic field in order to describe the electromagnetic effects associated with electrical currents flowing within rocks. The resulting system of equations is solved numerically and it is seen that a volume of rock may act as a diode that produces transient currents when it switches bias. These unidirectional currents are expected to produce transient unipolar magnetic pulses similar in form, amplitude, and duration to those observed before earthquakes, and this suggests that the pulses could be the result of geophysical semiconductor processes.

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“…However, since previous studies do not show strong evidence of correlation between the presumed magnetic precursors and seismic events, many scientists do not agree that these signals are really related to the earthquake occurrence. As a consequence, these researchers seriously put into question previous observations of magnetic ULF earthquake precursors and have published their findings (see Campbell, 2009;Masci, 2010Masci, , 2011aMasci, , b, 2012aThomas et al, 2009a, b) giving rise to an intense re-examination process of controversial scientific claims (see also Fraser-Smith et al, 2011;Masci, 2012d;Thomas et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…Several reports (see e.g. Hayakawa et al, 1999Hayakawa et al, , 2000Smirnova et al, 2001;Smirnova and Hayakawa 2007;Gotoh et al, 2003Gotoh et al, , 2004Ida and Hayakawa, 2006) by means of mono-fractal analysis document the observation of precursory signatures in the ULF geomagnetic field before the occurrence of strong earthquakes. According to Masci (2010), these authors reach their conclusions in an oversimplified manner failing to examine the influence of other possible ULF sources as well as the geomagnetic activity which is the main source of ULF disturbances (McPherron et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

On the multi-fractal characteristics of the ULF geomagnetic field before the 1993 Guam earthquake

Masci

2013

Nat. Hazards Earth Syst. Sci.

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Abstract. Ida et al. (2005) document significant changes in the multi-fractal parameters of the ULF geomagnetic field H component starting about one month before the 1993 Guam earthquake. According to the authors, these multi-fractal signatures can be considered as precursory signals of the Guam earthquake. As a consequence, they conclude that the multifractal analysis may have an important role in the development of short-term earthquake prediction capabilities. Since this and other similar reports have motivated the idea that earthquake prediction based on electromagnetic precursory signals may one day become a routine technique, the presumed precursors need to be validated through independent datasets. In this review the seismogenic origin of the multifractal magnetic signatures documented by Ida et al. (2005) before the 8 August 1993 Guam earthquake is seriously put into question. By means of the geomagnetic K p index, it is demonstrated that these multi-fractal parameter changes are normal signals induced by the variation of the global geomagnetic activity level.

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Comment on “Natural magnetic disturbance fields, not precursors, preceding the Loma Prieta earthquake” by Wallace H. Campbell

Abstract: Key Points We measured large‐amplitude mag fields prior to the Loma Prieta earthquake Campbell argues that these fields were merely natural magnetic disturbance fields We show that his arguments are false

Cited by 10 publications

References 25 publications

Are there new findings in the search for ULF magnetic precursors to earthquakes?

Are there new findings in the search for ULF magnetic precursors to earthquakes?

Pre-earthquake magnetic pulses

On the multi-fractal characteristics of the ULF geomagnetic field before the 1993 Guam earthquake

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