International Journal of Geosciences, 2012, 3, 1084-1088 http://dx.doi.org/10.4236/ijg.2012.35109 Published Online November 2012 (http://www.SciRP.org/journal/ijg) Spatial Distribution of Seismicity: Relationships with Geomagnetic Z-Component in Geocentric Solar Magnetospheric Coordinate System Galina Khachikyan 1 , Alexander Inchin 2 , Anatoly Lozbin 2 1 Institute of Seismology, Almaty, Kazakhstan 2 Institute of Space Techniques and Technologies, Almaty, Kazakhstan Email: khachikjan@seismology.kz Received July 21, 2012; revised August 23, 2012; accepted September 23, 2012 ABSTRACT For 173,477 epicenters of earthquakes with М ≥ 4.5, which occurred at the globe in 1973-2010, the geomagnetic Z- component in Geocentric Solar Magnetospheric (GSM) coordinate system were evaluated for the moment of earthquake occurrence on the base of the International Geomagnetic Reference Field model (IGRF-10). It is found that in the re- gions, where the Z GSM reaches large positive value (low and middle latitudes), earthquake occurrence is higher than in the regions where Z GSM is mainly negative (high latitudes). In the area of strongest seismicity at the globe, which is lo- cated in the longitudinal ranges of about 120˚E - 170˚W, the values of Z GSM are the most high at the globe. It is found that statistically significant dependence, with correlation coefficient R = 0.91, exists between the maximal possible magnitude of earthquake (M max ) and the logarithm of absolute value of Z GSM . We suggest that earthquake occurrence is triggered by the perturbations, which in first occur at the magnetopause due to reconnection of the magnetic field of the solar wind with the Earth’s magnetic field, and then propagate into the solid earth via the GEC, which is considered at present as a main applicant for a physical mechanism of solar-terrestrial relationships. It is clear that much work re- mains to further verify this speculative assertion and to find the physical processes linking seismicity with the main geomagnetic field structure. Keywords: Earthquake Occurrence; Earthquake Magnitude; Main Geomagnetic Field; Geocentric Solar Magnetospheric Coordinate System 1. Introduction From the beginning of the space age, the satellites ob- tained a lot of evidences on the electromagnetic effects in the near space plasma parameters prior major earth- quakes [1]. To explain that findings, an idea was ad- vanced [2] that the generation mechanism of electro- magnetic effects of earthquakes is a modification of the electric field in the Global Electric Circuit (GEC) due to earthquake preparation. The classical concept of GEC, firstly suggested in [3], presents a system of stationary electric currents between the ground and the ionosphere driven by the global thunderstorm activity [4]. Recently, the idea of electric coupling between the ionosphere and earthquake region was successfully used in [5] to explain the changes in the natural extremely low-frequency radio noise observed in the topside ionosphere aboard the DEMETER satellite at night, before major earthquakes. As in any electric circuit the electromagnetic perturbation in one region affects another regions, one may speculate that not only the state of near space plasma responds to electromagnetic perturbation in the lithosphere, as it is suggested in [2,5], but and vice versa, the lithosphere re- sponds to electromagnetic perturbation in the near space plasma up to the upper boundary of the GEC. At present, the GEC is considered as a main applicant for the me- chanism of solar-terrestrial coupling [4,6], and it is be- lieved [7,8] that its upper boundary may be located at the magnetopause, where the reconnection of the solar wind magnetic field with the earth’s magnetic field occur. The effectiveness of magnetic reconnection [9] depends on value and orientation of Z- components in both the solar wind magnetic field and Earth’s magnetic field as esti- mated in the Geocentric Solar Magnetospheric (GSM) coordinate system [10]. The most effective reconnection occur when the Z GSM -component for solar wind mag- netic field is large and negative, while the geomagnetic Z GSM -component is large and positive [9]. As the geo- magnetic Z GSM -component shows noticeable spatial and temporal variations, we check up in present paper if a pattern of spatial variation of seismicity shows any simi- Copyright © 2012 SciRes. IJG