The search for the Slichter mode: comparison of noise levels of superconducting gravimeters and investigation of a stacking method

Rosat, Séverine; Hinderer, J.; Crossley, David; Rivera, Luis

doi:10.1016/j.pepi.2003.07.010

Cited by 67 publications

(64 citation statements)

References 26 publications

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“…The necessity to correct seismometer and SG data for local atmospheric pressure at frequencies below 1 mHz has been demonstrated by many authors [e.g., Zürn and Widmer, 1995;Freybourger et al, 1997;Rosat et al, 2003a]. We first compare this earthquake to the 2001 Peruvian event.…”

Section: Introductionmentioning

confidence: 99%

High‐resolution analysis of the gravest seismic normal modes after the 2004 M_w = 9 Sumatra earthquake using superconducting gravimeter data

Rosat

2005

Geophysical Research Letters

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[1] The M w > 9 Sumatra-Andaman earthquake on December 26, 2004 has strongly excited the lowfrequency seismic modes and is a unique opportunity to improve the frequency and damping measurements of the gravest seismic modes. The precise estimation of the frequency splitting of the seismic modes below 1 mHz is needed to improve 1D-density models of the Earth. From this event, 2 S 1 is observed for the first time without any stacking on both SG (Superconducting Gravimeter) and seismic records. We report here analyses of SG data obtained from 11 sites. The spectra of SG records clearly show the splitting of 0 S 2 into 5 completely resolved singlets and the splitting of 0 S 3 into 7 singlets at individual stations. The present results demonstrate that SGs provide high quality data for a precise analysis of the low-frequency seismic modes.

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Section: Introductionmentioning

confidence: 99%

High‐resolution analysis of the gravest seismic normal modes after the 2004 M_w = 9 Sumatra earthquake using superconducting gravimeter data

Rosat

2005

Geophysical Research Letters

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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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“…The Seismic Noise Magnitude (SNM) concept, similar to the earthquake magnitude, is introduced in this procedure to quantify and compare the noise levels at seismic frequencies. Following nearly the same procedure, the OSG-057 noise level in the sub-seismic band is computed with respect to the term Sub-Seismic Noise Magnitude (SSNM) (Rosat et al 2003(Rosat et al , 2004Rosat and Hinderer 2011) generalized from SNM. Based on this method, Rosat et al (2003Rosat et al ( , 2004 enabled the quantitative comparison of SG noise levels at the GGP/IGETS stations in these two bands.…”

Section: The Methods and Resultsmentioning

confidence: 99%

OSG-057 Superconducting Gravimeter Noise Levels in Lhasa (China)

Zhang¹,

Xu²,

Sun³

et al. 2016

Terr. Atmos. Ocean. Sci.

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This research tests OSG-057 superconducting gravimeter (SG) performance in Lhasa in terms of noise levels in the seismic (2 min to 1 h), sub-seismic (1 to 6 h), and tidal (above 6 h) bands. Based on the Seismic Noise Magnitude (SNM) and Sub-Seismic Noise Magnitude (SSNM), 0.867 and 2.608 respectively, and compared to the noise levels of other SGs in the Global Geodynamics Project (GGP)/International Geodynamics and Earth Tide Service (IGETS), it is concluded that the instrument-site combination in Lhasa has low noise and good quality in both the seismic and sub-seismic bands. The seismic and sub-seismic band results were confirmed by large signal-to-noise ratio amplitude spectra observations below 1 milliHertz (mHz) obtained from OSG-057 data record residuals after the 4/11/2012 M8.6 Sumatra earthquake, and by background free Earth oscillation observations ('hum'), although very weak. Using the ETERNA Earth Tide Analysis program in the tidal band, it was found that the OSG-057 performs well due to the low average noise amplitudes and small standard deviations. Knowledge of the noise levels of the OSG-057 SG in Lhasa in different frequency bands provides a necessary precondition and reference for its applications to both global and regional geodynamical researches.

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The search for the Slichter mode: comparison of noise levels of superconducting gravimeters and investigation of a stacking method

Cited by 67 publications

References 26 publications

High‐resolution analysis of the gravest seismic normal modes after the 2004 M_w = 9 Sumatra earthquake using superconducting gravimeter data

High‐resolution analysis of the gravest seismic normal modes after the 2004 M_w = 9 Sumatra earthquake using superconducting gravimeter data

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

OSG-057 Superconducting Gravimeter Noise Levels in Lhasa (China)

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The search for the Slichter mode: comparison of noise levels of superconducting gravimeters and investigation of a stacking method

Cited by 67 publications

References 26 publications

High‐resolution analysis of the gravest seismic normal modes after the 2004 Mw = 9 Sumatra earthquake using superconducting gravimeter data

High‐resolution analysis of the gravest seismic normal modes after the 2004 Mw = 9 Sumatra earthquake using superconducting gravimeter data

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

OSG-057 Superconducting Gravimeter Noise Levels in Lhasa (China)

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High‐resolution analysis of the gravest seismic normal modes after the 2004 M_w = 9 Sumatra earthquake using superconducting gravimeter data

High‐resolution analysis of the gravest seismic normal modes after the 2004 M_w = 9 Sumatra earthquake using superconducting gravimeter data