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Study of Magnetic-Precursory Signals to Large Earthquakes: Jeremy N. Thomas

Project Title: Study of Magnetic-Precursory Signals to Large Earthquakes
Mendenhall Fellow: Jeremy N. Thomas, (303) 273-8487,
Duty Station: Golden, CO
Start Date: March 30, 2007
Education: Ph.D. (Earth and Space Sciences), University of Washington, 2005
Research Advisor: Jeffrey J. Love, (303) 273-8540,

Project Description: A direct correlation between earthquake activity and electromagnetic radiation has been observed by numerous researchers. However, the existence of electromagnetic-precursory events to earthquakes, which occur well before the seismic activity, have yet to be verified or dismissed within the scientific community. Because earthquakes are a major hazard to civilization, predicting them would benefit most of the Earth’s inhabitants. However, we need to be responsible in pushing ahead on this frontier, making a full exploration of alternative and, frankly, more conventional explanations of reported precursors.

Enhanced electromagnetic radiation precursory to earthquakes in the ultra-low frequency (ULF) to low frequency (LF) range (0.01 Hz - 100 kHz) have been reported by various researchers. ULF magnetic field variations precursory to the 1989 Loma Prieta earthquake reported by Fraser-Smith and others (1990) are the most suggestive evidence that precursory electromagnetic radiation is a real geophysical phenomenon. Other possible ULF precursors measured by ground-based magnetometers have been reported more recently prior to the Kobe, Japan, earthquake, the Chi-Chi earthquake in Taiwan, and the Biak, Indonesia, earthquake. In addition to these ground-based measurements, researchers have attempted to find precursory ULF radiation with satellite-borne magnetometers. Although no conclusive events were found during these satellite searches, new satellite programs have been initiated, such as the U.S.-based QuakeSat launched in 2003 and the French satellite DEMETER launched in 2004, to study precursory electromagnetic signals.

The purpose of this Mendenhall project is to conduct a critical examination of existing precursor reports, focusing first on the ground-based data from events, such reported by Fraser-Smith and others (1990) for Loma Prieta and then on the space-based data. If the reports of low-frequency electromagnetic precursory signals to large earthquakes are shown to be consistent and if the observations are reproducible, then this subject would, quite simply, be of extreme importance. However, uniquely identifying this ULF to LF radiation as precursory activity to earthquakes is difficult since magnetospheric, ionospheric, and thunderstorms processes radiate at these frequencies. The study will include an assessment of these other sources of low-frequency electromagnetic radiation in order to more objectively determine whether ULF to LF waves can, in fact, be practically used for earthquake prediction. A useful by-product of this work will be an enhanced fundamental understanding of magnetospheric, ionospheric and thunderstorm phenomena that can be studied with U.S. Geological Survey Geomagnetism Program data products.


Fraser-Smith, A., Bernardi, A., McGill, P., Ladd, M., Helliwell, R., and Villard, O., Jr., 1990, Low-frequency magnetic field measurements near the epicenter of the Ms 7.1 Loma Prieta earthquake: Geophysical Research Letters, v. 17, no. 9, p. 1465–1468.

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