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Is global seismicity signed by the Markowitz wobble ?
Type
Conference paper
Language
English
Obiettivo Specifico
1T. Geodinamica e interno della Terra
Status
Unpublished
Conference Name
Issued date
April 2008
Conference Location
Vienna
Abstract
For the past 108 years the worldwide occurrence of large seismic events shows a significant
cyclic temporal pattern of about 34 years. The spectral analysis of the irregular Earth's polar
motion over the last 108 years filtered from the secular drifts shows that both LOD and polhody
are affected by the same significant periodicity. The third amplitude of polar motion at decadal
periodicity in the terrestrial reference frame, after the Chandler and annual, is known as
Markowitz wobble.
The spectral coherence between the seismicity and polar motion is high at long periods, reaching
saturation value at about 20 years. No significant delay is shown by the cross-correlation analysis
between LOD, polhody and seismicity. If we accept the idea that global seismicity and polar motion are both signed by
the Markowitz wobble, we can infer that they could be modulated by the same
cause. Recent models hypothesize a gravitational and inertial coupling between the
mantle and an inner core able to reproduce the Markowitz wobble on the
polar motion. However, if the wobble signature on seismicity will be
confirmed, this interpretation should probably be revised
cyclic temporal pattern of about 34 years. The spectral analysis of the irregular Earth's polar
motion over the last 108 years filtered from the secular drifts shows that both LOD and polhody
are affected by the same significant periodicity. The third amplitude of polar motion at decadal
periodicity in the terrestrial reference frame, after the Chandler and annual, is known as
Markowitz wobble.
The spectral coherence between the seismicity and polar motion is high at long periods, reaching
saturation value at about 20 years. No significant delay is shown by the cross-correlation analysis
between LOD, polhody and seismicity. If we accept the idea that global seismicity and polar motion are both signed by
the Markowitz wobble, we can infer that they could be modulated by the same
cause. Recent models hypothesize a gravitational and inertial coupling between the
mantle and an inner core able to reproduce the Markowitz wobble on the
polar motion. However, if the wobble signature on seismicity will be
confirmed, this interpretation should probably be revised
References
Engdahl, E.R. and A. Villaseñor, Global Seismicity: 1900-1999, in W.H.K. Lee, H. Kanamori, P.C. Jennings, and C.
Kisslinger (editors), International Handbook of Earthquake and Engineering Seismology, Part A, Chapter 41, pp.
665-690, Academic Press, 2002.
Dunberry, M., 2008. Gravitational torque on the inner core and decadal polar motion, Geophys.J. Int., 172, 903-
920. Gross, R. S., I. Fukumori, and D. Menemenlis (2005), Atmospheric and oceanic excitation of decadalscale
Earth orientation variations, J. Geophys. Res., 110, B09405.
Varga, P., Gambis D., Bus Z., Bizouard C. 2005. The relationship between the global seismicity and the
rotation of the Earth. In: proceedings of Systémes de référence spatio-temporales, Observatoire de
Paris, 115-120.
Kisslinger (editors), International Handbook of Earthquake and Engineering Seismology, Part A, Chapter 41, pp.
665-690, Academic Press, 2002.
Dunberry, M., 2008. Gravitational torque on the inner core and decadal polar motion, Geophys.J. Int., 172, 903-
920. Gross, R. S., I. Fukumori, and D. Menemenlis (2005), Atmospheric and oceanic excitation of decadalscale
Earth orientation variations, J. Geophys. Res., 110, B09405.
Varga, P., Gambis D., Bus Z., Bizouard C. 2005. The relationship between the global seismicity and the
rotation of the Earth. In: proceedings of Systémes de référence spatio-temporales, Observatoire de
Paris, 115-120.
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