Materials of the International Conference
50th Anniversary of the International Geophysical Year
and Electronic Geophysical Year

16-19 September 2007 • Suzdal, Russia

Contribution of tidal forces into seismic process

B. V. Levin

Institute of the Marine Geology and Geophysics FED RAS, Yuzhno-Sakhalinsk, Russia

Abstract

It was recently shown that mechanical energy, annually transferred to 100-kilometer's layer of the litosphere by tidal forces of the Sun and the Moon amounts to about 1029 erg. In case of a simple model theoretical distribution of the tidal energy by the latitudinal belts of the Earth has typical bi-modal shape: two maximums at the latitudes of +45 and -45 degrees and zero values at both of the poles and at the equator. Distribution of the number of registered earthquakes against the area of latitudinal belts of the Earth shows zero values on the poles, local minimum at the equator and two maximums in the northern (35oN) and southern (10oS) hemispheres. According to data of E. V. Sasorova, earthquakes distribution density by the latitude in case of rationing of their numbers to the length of the margins of the litosphere plates gives distribution similar to theoretical distribution of the tidal energy. Analysis of the earthquakes catalogues shows that high seismic activity reveals in areas of high concentration of the tidal energy. It was found that not deep earthquakes (focus depth up to 70 km) are unevenly distributed through the months of the year, and probability of differentiation of this distribution from an even one is more than 0.99. The highest activation of the seismic process is observed in December, whereas the lowest is in April. This is true practically for all analyzed sub-regions of the Pacific basin (the Aleutian Islands, Alaska, Kamchatka, the Kuril Islands, Japan, Oceania and others, 31 sub-regions in total), including the Northern as well as the Southern hemispheres. It is shown that the growth of seismic activity in time coincides with the time when the Earth goes across the point of perihelion (minimal distance to the Sun) and this is when the value of tidal force increases by 6.3%. As a result of analysis of observed material, subdivided into magnitude ranges, depth intervals, geographical sub-regions, it was found that a non-random component is distinguished in the earthquake distribution between the Northern and the Southern hemispheres of the Earth. This effect can be related to the tidal impacts on the internal Earth core.

Citation: B. V. Levin (2007), Contribution of tidal forces into seismic process, in: Materials of the International Conference '50th Anniversary of the International Geophysical Year and Electronic Geophysical Year', GC RAS, Moscow, doi:10.2205/2007-IGY50conf.

© 2007 Geophysical Center RAS and authors


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