1. European Geosciences Union, General Assembly Vienna | Austria | 23–28 April 2017
Seismic zoning (first approximation) using data of the main geomagnetic field
Khachikyan G., Zhumabayev B., Toyshiev N., Kairatkyzy D., Seraliyev A., Khassanov E.
Institute of Ionosphere Almaty, Kazakhstan
Abstract EGU Session SM1.1 General Contribution on Earthquake
Figure 5 shows that ZGSM values are more strong in equatorial eastern hemisphere (5b) in comparison with the western hemisphere (5a). This may be a reason of the most strong seismicity at the globe namely in the eastern hemisphere (region of Sumatra, for example). Also, Figure 5 gives a hint that a maximal possible earthquake magnitude Mmax at any seismic region had to vary with time and season because ZGSM shows such variations.
Conclusion. It is possible to estimate maximal possible earthquake magnitude (Mmax) for any seismic region on the base of maximal possible geomagnetic ZGSM component. This allows one to carry out global seismic zoning (in first approximation) on the base of the main geomagnetic field data. Empirical relations between Mmax and {log[abs(ZGSM)]} may be used for prediction of earthquake magnitude if the place and time of future earthquake are already predicted.
References
[1] Khachikyan G., Inchin A., Lozbin A. Spatial distribution of seismicity: relationships with geomagnetic Z-component in geocentric solar magnetospheric coordinate system. International Journal of Geosciences – V.3. – № 5. – P
[2] Global NEIC catalog for
[3] Tsyganenko N. A. Geopack: A Set of Fortran Subroutines for Computations of the Geomagnetic Field in the Earth’s Magnetosphere,”
[4] The International Geomagnetic Reference Field model.
Introduction. Seismic zoning is among the most complicated and extremely important problems of modern seismology. In solving this problem, a very important parameter is the maximal possible earthquake magnitude (Mmax) which is believed at present depends on horizontal size of geoblocks. In addition to this opinion, it was found in [1] that Mmax value in any seismic region may be determined using ZGSM value that is geomagnetic Z-component estimated in geocentric solar-magnetosphere coordinate system (GSM). In that paper, an empirical relation between ZGSM and Mmax was obtained for the case of the whole planet. In this report we present empirical relations for some local regions with different types of tectonics.
Data
Data on earthquakes with М ≥ 4.5 occurred at the globe in were taken from the global NEIC catalog [1]. For the each of the epicenters, the value of the geomagnetic Z component in Geocentric Solar Magnetospheric) coordinate system (ZGSM) was calculated with using the FORTRAN subroutines Geopack [3] and the International Geomagnetic Reference Field model (IGRF-10) [4].
Results 
Figure 1 presents the result from [2] that is a scatter plot of the magnitude of earthquakes occurred at the globe in yrs versus {log[abs(ZGSM)]} in epicenter. Black lines show an envelope of maximal magnitude in sequential bins of 0.15 size, and a red solid line is the linear fit to envelope. Approximation relation between {log[abs(ZGSM)]} and maximal magnitude (fit to envelope) is shown in the capture to Figure 1. Investigations in more details showed that the coefficients of the regression equation are different for regions with different type of tectonics (Figures 2-4). Comparison of figures 2-4 shows that the most prominent correlation between {log[abs(ZGSM)]} and Mmax with correlation coefficient R=0.97 takes place in the region of the strongest seismicity at the globe in the eastern hemisphere (Figure 4).
Discussion 
The relationship between the intensity of the main geomagnetic field and released seismic energy is expectable, because both the main geomagnetic field and the tectonic activity of the planet are related somehow to the same source - the convection in the Earth’s liquid core. The relationship between earthquake magnitude and geomagnetic Z - component estimated namely in geocentric solar magnetosphere coordinate system (GSM), in which the interaction of the solar wind magnetic field with the geomagnetic field is better ordered, evidently points on the external (triggering) earthquake occurrence in the extremely stressed rock media. Interestingly, the value of geomagnetic ZGSM component for geographical region varies rather strongly with time and seasons. Figure 5 presents, for example, diurnal ZGSM variations for different months at the geographic equator but for two longitudes: 90˚W and 90˚E (5a, 5b, respectively).
Figure 1. A scatter plot of the magnitude of earthquakes with M≥4.5 occurred at the globe in yrs. Black solid line is an envelope of maximal magnitude in sequential bins of 0.15 size, and a red solid line is the linear fit to envelope as follows: Mmax=(5,22±0,17)+(0,78±0,06){log[abs(ZGSM)]}, with correlation coefficient R=0.91, standard deviation SD=0.56, and probability 95% [1].
Figure 2. The same as in Figure 1 only for the local region of the San Andreas Fault, defined by the coordinates 300N-450N, 1050W -1350W. The linear fit to the envelope is as follows (red line):
Mmax = (4,04 ± 0.38) + (0.7 ± 0.13) log[abs(ZGSM)], with correlation coefficient R=0.91, SD=0.34, and
p = 95%.
Figure 5. The diurnal variations of geomagnetic ZGSM – component for different months at earth’s surface at latitude 00, longitudes 900W and 900E (a, b, respectively) for 2005 year [1].
Figure 3. The same as in Figure 1 only for the local region of inland seismicity in Eurasia defined by the coordinates 300N-450N, E. The linear fit to the envelope is as follows (red line):
Mmax = (12.44 ± 0.48) + (1,15 ± 0.2) log[abs(ZGSM)], with
R = 0.87, SD = 0.98, p = 95%.
Figure 4. The same as in Figure 1 only for the territory of the strongest seismicity in the world defined by the coordinates 200S-200N, 900E-1500E. The linear fit to the envelope is as follows (red line):
Mmax = ( ± 1.5) + (5.7 ±0.4) log[abs(ZGSM)] with
R = 0.97, SD = 0.4, p= 95%.