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.
Highlights
Kp index is a complex average of the measurements by 13 magnetic observatories around the world
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
April 2016 The diurnal variations of the geomagnetic fields for the last 4 days before the Kumamoto earthquake on April 14 2016, observed at the Kanoya Observatory, and catalogued at Kakioka Magnetic Observatory data [3], H, Z, F: horizontal, vertical and total component, respectively, D: magnetic declination; the magnetic storm starts with a SSC pulse, “First hit” marks the Kumamoto earthquake time
Summary
Kp index is a complex average of the measurements by 13 magnetic observatories around the world. It took a sharp downward turn about 2 hrs before the quake It turned up rapidly, marked as “First hit” in Figure 2(d), coinciding with the onset of the Kumamoto earthquake on April 14 2016 at 12:26 UT. Inspired by this coincidence as well as similar cases such as in the 1995 Great Hanshin earthquake of January 17 1995, known as the Kobe earthquake, and the 2011 Tohoku Earthquake, we analyzed the seismic data of thousands of earthquakes of M ≥ 6 in relation to the variations of the Kp index from 1932 to 2016 (USGS Earthquake Catalogue [1] GFZ Potsdam WDC data, Kp index [2])
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