Global superconducting gravimeter observations and the search for the translational modes of the inner core

Courtier, N.; Ducarme, B.; Goodkind, John M.; Hinderer, J.; Imanishi, Yuichi; Seama, Nobukazu; Sun, He; Merriam, J. B.; Bengert, B.; Smylie, D. E.

doi:10.1016/s0031-9201(99)00083-7

Cited by 84 publications

(108 citation statements)

References 8 publications

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“…It is now the best instrument to survey the temporal gravity variations in the world. It has the potential to detect almost all signatures with periods ranging from serveral seconds related to coseimic movements to several years related to the variations in the Earth's rotation, even the phenomena associated with the secular tectonic movements of local crust, such as the the Earth's free oscillations (Banka and Crossley 1999;Van Camp 1999;Lei et al 2005;Park et al 2005), the Earth's tides (Sun et al 2001;Xu et al 2004a), the load effects of barometric pressure (Sun and Lou 1998), the nearly diurnal resonance (Defraigne et al 1994;Xu et al 2002), translational oscilations of the solid inner core (Smylie 1992;Courtier et al 2000;Rosat et al 2003;Xu et al 2010), Polar motion (Loyer et al 1999;Xu et al 2004b), secular crust deformation due to earthquakes or other reasons Imanishi et al 2004;Richter et al 2004;Xu et al 2008) and so on. As a result, a significant scientific project, i.e., the Global Geodynamics Project, has been carried out since 1997 in order to investigate global and local dynamic problems using continuous gravity data from a worldwide network of superconducting gravimeters Crossley 2004;Crossley and Hinderer 2009).…”

Section: Introductionmentioning

confidence: 99%

Results of Gravity Observations Using a Superconducting Gravimeter at the Tibetan Plateau

Sun¹,

Xu²,

Chen³

et al. 2013

Terr. Atmos. Ocean. Sci.

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The tidal and nontidal gravity change characteristics in the Tibetan Plateau region were investigated using the continuous gravity measurements recorded with a superconducting gravimeter (SG) installed in Lhasa from December 8, 2009 to September 30, 2011. The results indicated that the precision of the tidal gravity observations with the SG in Lhasa was very high. The standard deviation of the harmonic analysis for the gravity tides was 0.498 nm s -2 , and the uncertainties of amplitude factors in the four main tidal waves (i.e., O 1 , K 1 , M 2 and S 2 ) were better than 0.002%. In addition, the diurnal gravity tide observations clearly revealed a pattern of nearly diurnal resonance. As a result, it is affirmed that the station should act as a local tidal gravity reference in the Tibetan Plateau and its adjacent regions. The load effects of oceanic tides are so weak that the resulting perturbation in the gravimetric factors is less than 0.6%. However, the load effects of the local atmosphere on either the tidal or the nontidal gravity observations are significant, although no seasonal variations have been found. After removing the atmospheric effects, the standard deviation of the harmonic analysis for the gravity tides decreased obviously from 4.160 to 0.498 nm s -2 . Having removed the load effects of oceanic tides and local atmosphere, it is found that the tidal gravity observations are significantly different from those expected theoretically, which may be related to active tectonic movement and extremely thick crust in the Tibetan Plateau region. In addition, the Earth's free oscillations excited by 2011 Tohoku-Oki M w 9.0 Earthquake were successfully detected.

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Section: Introductionmentioning

confidence: 99%

Results of Gravity Observations Using a Superconducting Gravimeter at the Tibetan Plateau

Sun¹,

Xu²,

Chen³

et al. 2013

Terr. Atmos. Ocean. Sci.

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“…Jensen et al 1995;Hinderer et al 1995;Kroner et al 2004;Sun et al 2006;Rosat et al 2007) even though some scientists already claimed their detection (e.g. Smylie 1992;Courtier et al 2000;Xu et al 2010). The search for the detection of the Slichter modes of the Earth still continues.…”

Section: Introductionmentioning

confidence: 99%

Period of the Slichter mode of Mercury and its possible observation

Coyette

Hoolst

Déhant

2012

A&A

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Aims. We study the period of the Slichter mode (vibrational mode of the inner core of a planet) of Mercury in relation to its interior structure and assess the possibility to observe this mode with the probes MESSENGER and BepiColombo. Methods. The methodology of Grinfeld & Wisdom (2005, Phys. Earth Planet. Int., 151, 77) for the determination of the period of the polar Slichter modes of a planetary interior consisting of three homogeneous layers is generalized to models with an arbitrary but finite number of layers. Slichter modes periods are calculated for a large set of interior structure models of Mercury. We study the possible excitation of Slichter modes by a colllision with a meteoroid and estimate the minimal size of the meteoroid that could lead to a detection of these modes by BepiColombo. Results. The Slichter mode period obtained is on the order of several hours. Observation of the Slichter mode of Mercury allows constraining the inner core. An impact by a meteoroid with a radius of at least 100 m could excite the Slichter mode to a level observable by BepiColombo (assuming that the Slichter mode is the only excited mode), but since the estimated damping time of the Slichter mode is well below the average time between impacts of at least that size such an impact must have occured recently (less than 0.5 My ago).

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“…That frequency range covers all the possible periods for the Slichter modes predicted or observed by the previous works (e.g. Smylie, 1992, Courtier et al 2000, Rieutord, 2002, Rogister, 2003.…”

Section: Application To the Search For The Slichter Modes In The Sub-mentioning

confidence: 85%

“…Smylie andMcMillan, 1998 andRieutord, 2002). However, many attempts using spectral methods and stacking processes have not yet led to the reliable detection of the surface gravity signature of the free oscillation of the inner core Hinderer et al, 1995;Rosat et al, 2003 and2006;Guo et al 2006a and2006b) while the unique observation by Smylie (1992) and Smylie et al (1993) has been confirmed by Courtier et al (2000). However, Rieutord (2002) and Rogister (2003) have demonstrated that this unique claim of detection is irrelevant to the theoretical predictions.…”

Section: Introductionmentioning

confidence: 99%

Application of a non-linear damped harmonic analysis method to the normal modes of the Earth

Rosat

Fukushima

Sasajima

et al. 2008

Journal of Geodynamics

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Global superconducting gravimeter observations and the search for the translational modes of the inner core

Cited by 84 publications

References 8 publications

Results of Gravity Observations Using a Superconducting Gravimeter at the Tibetan Plateau

Results of Gravity Observations Using a Superconducting Gravimeter at the Tibetan Plateau

Period of the Slichter mode of Mercury and its possible observation

Application of a non-linear damped harmonic analysis method to the normal modes of the Earth

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