Estimation of the asymmetric vertical variation of the southern and northern hemispheres of the Earth

Abstract

In previous studies, the northern hemisphere of the Earth is considered to be in compression while the southern one is in expansion. In this study, based on three different methods, we calculate average vertical variations of the two hemispheres from velocity field data under the ITRF2008 (International Terrestrial Reference Frame 2008) solution. Results show that the northern hemisphere is in expansion at the rate about 1 mm/yr, while the compression rate of the southern hemisphere is one order smaller than the expansion rate of the northern one. After the post glacial rebound effect is subtracted, results show that the expansion and compression rates of the northern and southern hemispheres are 0.46 mm/yr and -0.19 mm/yr, respectively. Transformation between the velocity fields under ITRF2008 and ITRF2000 can explain why different authors have different conclusions about the expansion/compression pattern of one hemisphere or the other. Anyway, the entire Earth is expanding at a rate about 0.2 mm/yr, and this estimation coincides with results of our previous studies. The mean variation rates of the radii at different latitudes have been calculated.

Indications from space geodesy, gravimetry and seismology for slow Earth expansion at present – comment on “The Earth expansion theory and its transition from scientific hypothesis to pseudoscientific belief” by Sudiro (2014)

“…The expansion rates found are in the range of 0.1-0.4 mm yr −1 (Wu et al, 2011;Shen et al, 2011Shen et al, , 2015a, not far from the traditional slow expansion rate of 0.5 mm yr −1 . Much of the new work is being done in China, where it seems that a more open attitude towards the possibility of Earth expansion exists.…”

“…This was consistent with a possible true velocity of CM of 0.5-1.0 mm yr −1 relative to that in ITFR2008. In the same vein, Shen et al (2015a) noted that the origin of ITFR2008 is moving southward relative to that of ITFR2000 at the rate of 1.8 mm yr −1 . When this southward trend of CM was subtracted from the vertical velocities of all stations, the Southern Hemisphere was seen to be expanding at a rate of 0.71 mm yr −1 , while the Northern Hemisphere was contracting at −0.44 mm yr −1 .…”

“…A truly geocentric frame would instead fix the origin of the frame permanently in the Earth's CM. However, to estimate long-term trends in expansion and contraction the ITRF system alone can suffice (Shen et al, 2015a).…”

“…Consequently, all stations cannot be weighted the same and ocean areas in particular tend to be neglected. This dependence on landbased stations to set up the ITRF potentially introduces a huge error in interpretation of results, as expansion could be occurring asymmetrically in one hemisphere or the other (Shen et al, 2015a). Secondly, many stations are located on active orogen belts or at the edge of plate boundaries.…”

“…The only expansionist author they cited is Carey, a noted fast expansion proponent. Shen et al (2015a) later criticized the approach taken by Wu et al of estimating multi-parameters (plate rotations, Love numbers, expansion, etc.) simultaneously.…”