TITLE:
Geomagnetic Kp Index and Earthquakes
AUTHORS:
Nobuo Urata, Gerald Duma, Friedemann Freund
KEYWORDS:
Geomagnetic, Earthquake, Kp Index, Magnetic Storm, Lorentz Force
JOURNAL NAME:
Open Journal of Earthquake Research,
Vol.7 No.1,
February
12,
2018
ABSTRACT:
In the ionosphere, the solar winds generate electrical currents. On the Earth
surface, these currents cause magnetic field fluctuations. These fluctuations,
penetrating the Earth interior, induce the electrical currents J, and, in the
presence of the Earth magnetic field B, generate electromagnetic force, known
as Lorentz force F = J × B. To study the relation of earthquakes and the Lorentz
force, acting at the near onset times of strong earthquakes, we examine
the Kp index, a logarithmic measure of the magnetic field deviation. The time
varying Kp index gives us J, which in turn determines F. The variations of the
Kp index were stacked by aligning their central times to the times of main
earthquake shocks. This stacking method has been a popular and powerful
tool in image processing, because it lifts up only the geomagnetic effect like
carving a relief. The Lorentz force tilts the subtle force balance in the earth
crust towards triggering the release of stress strain energy, initiating an
earthquake in a similar way as a mountain climber’s step can trigger the avalanches.
The internal dynamics, however, are highly statistical. Conventional
statistical methods are used in combination with a newly devised method,
which compares the time sequences of hypothetical random earthquakes to
real ones. We find that the distinctive patterns of the Kp surges often strongly
correlate to the onset of earthquake. This correlation depends on the seismic
regions and the magnitudes of earthquakes. The stronger the earthquake is,
more closely the Kp surge is associated. The statistical significance of nearly
100% is obtained for the Kp variations, synchronizing with more earthquakes
in the Pacific Rim region. In parallel with the data analysis the historical
studies are reviewed. The solar activities have been considered to influence
the earthquake occurrences and the relation of the two has been studied extensively
in the recent years as well as in the past century. A comprehensive
list of publications is created with the brief introductions for each in the last
chapter.