Abstract
Removal of the electrical shielding from a type of Fourier transform seismometer overlays seismic information with Extremely Low Frequency-range (ELF) electromagnetic signals between about 0.3 Hz and 36 Hz (the ITU-designated range of ELF is 3 to 30 Hz). The observed signals originate in the electric power grid, shown clearly by the fact that they are sum and difference heterodyne products with the power grid’s higher harmonics of 60 Hz, typically the 36th and 37th, because the seismometer’s chosen frequency modulation (FM) carrier frequency is roughly 2200 Hz. It is especially interesting that on 2017-03-19, prior to 14:25:12 UTC, the instrument recorded an 11 minute sequence of 20.3 Hz ELF outbursts that culminated intimately with a 3.2 magnitude earthquake located a few miles west of Bardwell KY. These ~20.3 Hz ELF signals, very near the third Schumann resonance frequency, have been recorded numerous times. They are distinctive and fairly strong, ranging 15 to 30 db or more above the noise floor, but definitely not an every-day event; months can pass without them. So far most of these ELF signals do not have an intimately associated earthquake, with the event of 2017-03-19 being one of only two exceptions recorded thus far. That quake’s location was more than one hundred miles from the instrument, in the New Madrid Seismic Zone (NMSZ). The second case, a quake in Kansas, was about three times farther from the instrument, and its ELF signals were correspondingly weaker. Those other, unassociated electromagnetic events might come from quakes too weak to detect, but it should be noted that stronger, easily detected quakes also rarely exhibit any ELF/seismic “connectivity”. This paper describes an instrument that overlays ELF, electric field and seismic signals. The instrument’s two-dimensional (2D) output has a time axis (horizontal) resolution of ~3 seconds and an ELF frequency (vertical) resolution of ~0.3 Hz.
Highlights
In February of 2011, a magnitude 4.7 Arkansas earthquake shook Cotter Arkansas, where the author of this paper lives
This paper describes an instrument that overlays ELF, electric field and seismic signals
Results and Discussion (Figure 8) illustrates one specific type of man-made, ELF-range signal that was recorded by the multivariable FM seismometer during the final military years of HAARP
Summary
In February of 2011, a magnitude 4.7 Arkansas earthquake shook Cotter Arkansas, where the author of this paper lives. The grid’s partially power saturated transformers are non-linear devices, able to create excessive harmonics of the fundamental frequency if not at least partially corrected for non-linearity of its loads; the possibility for heteodyne mixing of the 60 Hz harmonics with incoming ELF signals is worth considering [1] This viewpoint is offered as a reasonable explanation for the observed man-made HAARP signals as well as the occasional, apparently natural signals near Schumann resonant frequencies, both of which are picked up by the power grid, but the concept needs quantitative verification, perhaps using numerical electromagnetic code or similar computations [2]. The detection range of lightning electrometric effects was only about 15 miles based on flash to thunder times This phenomenon apparently isn’t a power grid effect, but rather, is due to the single wire signal link floating between field effect electronic components of the seismometer and in the computer’s sound card.
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