DOCSLIB.ORG

Inversion of Polar Motion Data: Chandler Wobble, Phase Jumps, and Geomagnetic Jerks Dominique Gibert, Jean-Louis Le Mouël

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Inversion of Polar Motion Data: Chandler Wobble, Phase Jumps, and Geomagnetic Jerks Dominique Gibert, Jean-Louis Le Mouël Inversion of polar motion data: Chandler wobble, phase jumps, and geomagnetic jerks Dominique Gibert, Jean-Louis Le Mouël To cite this version: Dominique Gibert, Jean-Louis Le Mouël. Inversion of polar motion data: Chandler wobble, phase jumps, and geomagnetic jerks. Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2008, 113 (B10), pp.B10405. 10.1029/2008JB005700. insu-00348004 HAL Id: insu-00348004 https://hal-insu.archives-ouvertes.fr/insu-00348004 Submitted on 1 Apr 2016 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, B10405, doi:10.1029/2008JB005700, 2008 Inversion of polar motion data: Chandler wobble, phase jumps, and geomagnetic jerks Dominique Gibert1 and Jean-Louis Le Moue¨l1 Received 18 March 2008; revised 11 July 2008; accepted 24 July 2008; published 23 October 2008. [1] We reconsider the analysis of the polar motion with a method totally different from the wavelet analysis used in previous papers. The total polar motion is represented as the sum of oscillating annual and Chandler terms whose amplitude and phase perturbations are inverted with a nonlinear simulated annealing method. The phase variations found in previous papers are confirmed with the huge phase change (3p/2) occurring in the 1926–1942 period and another less important one (p/3) in the 1970–1980 epoch. The best Chandler period, Tc, is found to be 434 ± 0.5 mean solar days. The epochs of significant phase changes found in the Chandler wobble are also those where important geomagnetic jerks occur in the secular variation of the geomagnetic field. Turbulent viscous friction produced by small-scale topography at the core-mantle boundary might be responsible for the observed phase jumps. Citation: Gibert, D., and J.-L. Le Moue¨l (2008), Inversion of polar motion data: Chandler wobble, phase jumps, and geomagnetic jerks, J. Geophys. Res., 113, B10405, doi:10.1029/2008JB005700. 1. Introduction and constitutes a new clue to the role of core-mantle coupling onto the Earth’s polar motion. [2] The movement of the Earth’s pole has been observed [4] In the present paper, we reconsider the analysis of the for more than 150 years, and, at the end of the 19th century, Earth’s polar motion with a new method totally different Chandler [1891a, 1891b] showed that this motion is the from the wavelet analysis used in our earlier papers [Gibert sum of two periodic oscillations, the forced annual oscilla- et al., 1998; Bellanger et al., 2002]. Also, the inverse tion and the Chandler wobble with a period close to 434 approach followed in the present study is more direct in mean solar days [e.g., Guinot, 1972; Lambeck, 1980; Wahr, the sense that the detrended total polar motion is analyzed 1988; Cazenave and Feigl, 1994]. Both the amplitude and without the complicated preprocessing stages of the wavelet the phase of the Chandler wobble vary with time [e.g., analysis. Moreover, we hope this new and simpler method Lambeck, 1980], and Danjon and Guinot [1954] first will be more easily used by independent teams in order to reported a phase change of about 150° which occurred perform analysis similar to the one presented here. around 1926 and was achieved in less than 10 years [5] In the remaining of the present paper, we first present [Guinot, 1972]. This phase jump remained poorly docu- the polar motion series and describe the model used to mented until other jumps were reported by Gibert et al. compute realistic synthetic series to be compared with the [1998] and suggested to be in temporal coincidence with data. Then, we detail the parameterization of the inverse geomagnetic jerks [Gibert et al., 1998; Bellanger et al., problem where the amplitudes of the annual and Chandler 2002]. Similar phase jumps have been detected in the Free components of the polar motion are to be retrieved together Core Nutation time series and also found in coincidence with the phase curve of the Chandler term. Next, the with geomagnetic jerks [Shirai et al., 2005]. nonlinear inversion is performed with the simulated anneal- [3] Different hypotheses have been proposed as the ing method and a Bayesian assessment of the uncertainty excitation mechanism of the Chandler wobble (see Dehant attached to the estimated parameters is done with the and de Viron [2002] for a short review), the main ones being Metropolis algorithm. the atmosphere [e.g., Aoyama and Naito, 2001], the pres- sure at the bottom of the oceans [Gross, 2000; Brzezin˜ski and Nastula, 2002; Gross et al., 2003], the earthquakes 2. Modeling of the Polar Motion [Mansinha and Smylie, 1967; Gross, 1986], or core motions 2.1. Polar Motion Data [Wahr,1988;Dickman, 1993]). The proposed temporal [6] The total polar motion, m(t), provided by the Interna- coincidence between geomagnetic jerks and phase jumps tional Earth Rotation Service (IERS) (data series eopc01) is in the Chandler wobble constitutes an exciting challenge shown in Figure 1a. Let us recall that the coordinate system is left-handed with the X axis coinciding with the Green- wich meridian and the Y axis corresponding to the W90 1 meridian. This signal is the superimposition of a smooth Institut de Physique du Globe, CNRS/INSU UMR 7154, Paris, France. secular drift d(t) and of an oscillating term o(t) resulting Copyright 2008 by the American Geophysical Union. from interferences between the annual prograde and retro- 0148-0227/08/2008JB005700$09.00 grade components, ap(t) ar(t), and the prograde Chandler B10405 1of8 B10405 GIBERT AND LE MOUE¨ L: INVERSION OF POLAR MOTION DATA B10405 wobble c(t)[Lambeck, 1980]. In previous studies [Gibert et [10] As can be seen in equation (2), the amplitudes are al., 1998; Bellanger et al., 2002], we showed that the annual linear parameters, while the phase variation is a nonlinear prograde component is dominant with respect to the retro- one. In what follows, the inversion will not deal directly grade one which, however, remains significant (see the inset with these unknown functions, but instead will be per- in Figure 2c for an illustration of the importance of the formed for primary parameters from which the Apa(t), Ara(t), retrograde annual component). In the same studies, it was Ac(t) and Df(t) functions are deduced. More explicitly, the also shown that the Chandler wobble is affected by a small amplitude functions are obtained by linearly interpolating number of phase perturbations Df(t) whose temporal shape coarsely sampled amplitude functions. In practice, this reads may be modeled as sigmoid phase jumps with a short ÂÃÀÁÀÁÀÁ duration of the order of one year. Accounting for these ApaðÞ¼LIt Apa;1; t1 ; ÁÁÁ; Apa;k ; tk ; ÁÁÁ; Apa;N ; tN ; ð4Þ observations the total polar motion may be written as, ÂÃÀÁÀÁÀÁ mtðÞ¼otðÞþdtðÞþntðÞ AraðÞ¼LIt Ara;1; t1 ; ÁÁÁ; Ara;k ; tk ; ÁÁÁ; Ara;N ; tN ; ð5Þ ¼ apðÞþt arðÞþt ctðÞþdtðÞþntðÞ; ð1Þ ÂÃÀÁÀÁÀÁ where n(t) represents the noise presents in the data AcðÞ¼LIt Ac;1; t1 ; ÁÁÁ; Ac;k ; tk ; ÁÁÁ; Ac;N ; tN ; ð6Þ (Figure 1c). [7] In the present study we remove the secular drift before where LI represents the linear interpolation operator, and inverting the data. Owing to the smooth nature of d(t), we where the dates tk are fixed and regularly distributed with a represent it by the least squares fitted polynomials of degree sampling interval of 3 months. Consequently, for ampli- 5 shown in Figure 1a. No significant differences were tudes, the parameters to be actually determined are the observed when using either fourth and sixth degree poly- elements of the three sets {Apa,k, k =1,N}, {Ara,k, k =1,N}, nomials. The noisy oscillating part, o(t)+n(t), is obtained and {Ac,k, k =1,N}. by subtracting the fitted polynomials from the total polar [11] An identical parameterization is adopted for the motion and is shown in Figure 1b. phase variation function Df(t), [8] We remark that IERS data at face value, and the polar ÂÃÀÁÀÁÀÁÀÁ motion series shown in Figure 1a results from the merging 0 0 0 0 DfðÞ¼LIt Df1; t1 ; Df2; t2 ; ÁÁÁ; Dfk ; tk ; ÁÁÁ; DfM ; tM of series with data of different nature (for more details, see 7 IERS Web site http://www.iers.org). For instance, it cannot ð Þ be eliminated that some inconsistencies affect the data in the 0 1970–1980 period due to the merging of classical astrome- with the important difference that the dates t k are not fixed tric and space geodetic measurements [Gross and Vondra´k, but, instead, are to be determined together with the phase 1999]. variations Dfk. This parameterization makes the inversion highly non linear but, as will be seen later, it permits us to 2.2. Parameterization of the Polar Motion Model eventually represent the phase function with a very small [9] The signal to be inverted is the o(t) part of the total number M of parameters. polar motion and, in the present study, the model of signal [12] To summarize, the model to be determined is the set used in the forward problem reads, of parameters, ÈÉ M¼ A ; ÁÁÁ; A ; ÁÁÁ; A [paÈÉ;1 pa;k pa;N m 2ipt o ðÞ¼t ApaðÞt exp þ iDfpa Ara;1; ÁÁÁ; Ara;k ; ÁÁÁ; Ara;N Ta [ ÈÉ A ; ÁÁÁ; A ; ÁÁÁ; A 2ipt [ c;1 c;k c;N þ AraðÞt exp À À iDfra Ta fgDf1; ÁÁÁ; Dfk ; ÁÁÁ; DfM [ ÈÉ 2ipt 0 0 0 þ AcðÞt exp þ iDfðÞt ; ð2Þ t1; ÁÁÁ; tk ; ÁÁÁ; tM Tc [ ÈÉ Dfpa; Dfra ; ð8Þ where the real amplitudes Apa(t), Ara(t), Ac(t), the phase from which the functions Apa(t), Ara(t), Ac(t) and Df(t)are variation Df(t), and the constant phase shifts Dfpa, Dfra of the annual components are to be determined.
Load more

Recommended publications
  • Preliminary Estimation and Validation of Polar Motion Excitation from Different Types of the GRACE and GRACE Follow-On Missions Data
    remote sensing Article Preliminary Estimation and Validation of Polar Motion Excitation from Different Types of the GRACE and GRACE Follow-On Missions Data Justyna Sliwi´ ´nska 1,* , Małgorzata Wi ´nska 2 and Jolanta Nastula 1 1 Space Research Centre, Polish Academy of Sciences, 00-716 Warsaw, Poland; [email protected] 2 Faculty of Civil Engineering, Warsaw University of Technology, 00-637 Warsaw, Poland; [email protected] * Correspondence: [email protected] Received: 18 September 2020; Accepted: 22 October 2020; Published: 23 October 2020 Abstract: The Gravity Recovery and Climate Experiment (GRACE) mission has provided global observations of temporal variations in the gravity field resulting from mass redistribution at the surface and within the Earth for the period 2002–2017. Although GRACE satellites are not able to realistically detect the second zonal parameter (DC20) of geopotential associated with the flattening of the Earth, they can accurately determine variations in degree-2 order-1 (DC21, DS21) coefficients that are proportional to variations in polar motion. Therefore, GRACE measurements are commonly exploited to interpret polar motion changes due to variations in the global mass redistribution, especially in the continental hydrosphere and cryosphere. Such impacts are usually examined by computing the so-called hydrological polar motion excitation (HAM) and cryospheric polar motion excitation (CAM), often analyzed together as HAM/CAM. The great success of the GRACE mission and the scientific robustness of its data contributed to the launch of its successor, GRACE Follow-On (GRACE-FO), which began in May 2018 and continues to the present. This study presents the first estimates of HAM/CAM computed from GRACE-FO data provided by three data centers: Center for Space Research (CSR), Jet Propulsion Laboratory (JPL), and GeoForschungsZentrum (GFZ).
    [Show full text]
  • Chandler Wobble: Stochastic and Deterministic Dynamics 3 2 Precession and Deformation
    Chandler wobble: Stochastic and deterministic dynamics Alejandro Jenkins Abstract We propose a model of the Earth’s torqueless precession, the “Chandler wobble”, as a self-oscillation driven by positive feedback between the wobble and the centrifugal deformation of the portion of the Earth’s mass contained in circu- lating fluids. The wobble may thus run like a heat engine, extracting energy from heat-powered geophysical circulations whose natural periods would otherwise be unrelated to the wobble’s observed period of about fourteen months. This can ex- plain, more plausibly than previous models based on stochastic perturbations or forced resonance, how the wobble is maintained against viscous dissipation. The self-oscillation is a deterministic process, but stochastic variations in the magnitude and distribution of the circulations may turn off the positive feedback (a Hopf bifur- cation), accounting for the occasional extinctions, followed by random phase jumps, seen in the data. This model may have implications for broader questions about the relation between stochastic and deterministic dynamics in complex systems, and the statistical analysis thereof. 1 Introduction According to Euler’s theory of the free symmetric top, the axis of rotation precesses about the axis of symmetry, unless both happen to align [1]. Applied to the Earth, this implies that the instantaneous North Pole should describe a circle about the axis of symmetry (perpendicular to the Earth’s equatorial bulge), causing a periodic change in the latitude of any fixed
    [Show full text]
  • Redalyc.On a Possible Connection Between Chandler Wobble and Dark
    Brazilian Journal of Physics ISSN: 0103-9733 [email protected] Sociedade Brasileira de Física Brasil Portilho, Oyanarte On a possible connection between Chandler wobble and dark matter Brazilian Journal of Physics, vol. 39, núm. 1, marzo, 2009, pp. 1-11 Sociedade Brasileira de Física Sâo Paulo, Brasil Available in: http://www.redalyc.org/articulo.oa?id=46413555001 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Brazilian Journal of Physics, vol. 39, no. 1, March, 2009 1 On a possible connection between Chandler wobble and dark matter Oyanarte Portilho∗ Instituto de F´ısica, Universidade de Bras´ılia, 70919-970 Bras´ılia–DF, Brazil (Received on 17 july, 2007) Chandler wobble excitation and damping, one of the open problems in geophysics, is treated as a consequence in part of the interaction between Earth and a hypothetical oblate ellipsoid made of dark matter. The physical and geometrical parameters of such an ellipsoid and the interacting torque strength is calculated in such a way to reproduce the Chandler wobble component of the polar motion in several epochs, available in the literature. It is also examined the consequences upon the geomagnetic field dynamo and generation of heat in the Earth outer core. Keywords: Chandler wobble; Polar motion; Dark matter. 1. INTRODUCTION ence of a DM halo centered in the Sun and its influence upon the motion of planets; numerical simulations due to Diemand et al.
    [Show full text]
  • True Polar Wander: Linking Deep and Shallow Geodynamics to Hydro- and Bio-Spheric Hypotheses T
    True Polar Wander: linking Deep and Shallow Geodynamics to Hydro- and Bio-Spheric Hypotheses T. D. Raub, Yale University, New Haven, CT, USA J. L. Kirschvink, California Institute of Technology, Pasadena, CA, USA D. A. D. Evans, Yale University, New Haven, CT, USA © 2007 Elsevier SV. All rights reserved. 5.14.1 Planetary Moment of Inertia and the Spin-Axis 565 5.14.2 Apparent Polar Wander (APW) = Plate motion +TPW 566 5.14.2.1 Different Information in Different Reference Frames 566 5.14.2.2 Type 0' TPW: Mass Redistribution at Clock to Millenial Timescales, of Inconsistent Sense 567 5.14.2.3 Type I TPW: Slow/Prolonged TPW 567 5.14.2.4 Type II TPW: Fast/Multiple/Oscillatory TPW: A Distinct Flavor of Inertial Interchange 569 5.14.2.5 Hypothesized Rapid or Prolonged TPW: Late Paleozoic-Mesozoic 569 5.14.2.6 Hypothesized Rapid or Prolonged TPW: 'Cryogenian'-Ediacaran-Cambrian-Early Paleozoic 571 5.14.2.7 Hypothesized Rapid or Prolonged TPW: Archean to Mesoproterozoic 572 5.14.3 Geodynamic and Geologic Effects and Inferences 572 5.14.3.1 Precision of TPW Magnitude and Rate Estimation 572 5.14.3.2 Physical Oceanographic Effects: Sea Level and Circulation 574 5.14.3.3 Chemical Oceanographic Effects: Carbon Oxidation and Burial 576 5..14.4 Critical Testing of Cryogenian-Cambrian TPW 579 5.14A1 Ediacaran-Cambrian TPW: 'Spinner Diagrams' in the TPW Reference Frame 579 5.14.4.2 Proof of Concept: Independent Reconstruction of Gondwanaland Using Spinner Diagrams 581 5.14.5 Summary: Major Unresolved Issues and Future Work 585 References 586 5.14.1 Planetary Moment of Inertia location ofEarth's daily rotation axis and/or by fluc­ and the Spin-Axis tuations in the spin rate ('length of day' anomalies).
    [Show full text]
  • Earth Orientation Parameters from VLBI Determined with a Kalman Filter
    Originally published as: Karbon, M., Soja, B., Nilsson, T., Deng, Z., Heinkelmann, R., Schuh, H. (2017): Earth orientation parameters from VLBI determined with a Kalman filter. ‐ Geodesy and Geodynamics, 8, 6, pp. 396— 407. DOI: http://doi.org/10.1016/j.geog.2017.05.006 Geodesy and Geodynamics 8 (2017) 396e407 Contents lists available at ScienceDirect Geodesy and Geodynamics journal homepages: www.keaipublishing.com/en/journals/geog; http://www.jgg09.com/jweb_ddcl_en/EN/volumn/home.shtml Earth orientation parameters from VLBI determined with a Kalman filter * Maria Karbon a, , Benedikt Soja b, Tobias Nilsson a, Zhiguo Deng a, Robert Heinkelmann a, Harald Schuh a, c a GFZ German Research Centre for Geosciences, Telegrafenberg A17, Potsdam, Germany b Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA c Technical University of Berlin, Strabe des 17. Juni 135, Berlin, Germany article info abstract Article history: This paper introduces the reader to our Kalman filter developed for geodetic VLBI (very long baseline Received 24 November 2016 interferometry) data analysis. The focus lies on the EOP (Earth Orientation Parameter) determination Received in revised form based on the Continuous VLBI Campaign 2014 (CONT14) data, but also earlier CONT campaigns are 23 May 2017 analyzed. For validation and comparison purposes we use EOP determined with the classical LSM Accepted 24 May 2017 (least squares method) estimated from the same VLBI data set as the Kalman solution with a daily Available online 6 September 2017 resolution. To gain higher resolved EOP from LSM we run solutions which yield hourly estimates for polar motion and dUT1 ¼ Universal Time (UT1) e Coordinated Universal Time (UTC).
    [Show full text]
  • On a Possible Connection Between Chandler Wobble and Dark Matter
    Brazilian Journal of Physics, vol. 39, no. 1, March, 2009 1 On a possible connection between Chandler wobble and dark matter Oyanarte Portilho∗ Instituto de F´ısica, Universidade de Bras´ılia, 70919-970 Bras´ılia–DF, Brazil (Received on 17 july, 2007) Chandler wobble excitation and damping, one of the open problems in geophysics, is treated as a consequence in part of the interaction between Earth and a hypothetical oblate ellipsoid made of dark matter. The physical and geometrical parameters of such an ellipsoid and the interacting torque strength is calculated in such a way to reproduce the Chandler wobble component of the polar motion in several epochs, available in the literature. It is also examined the consequences upon the geomagnetic field dynamo and generation of heat in the Earth outer core. Keywords: Chandler wobble; Polar motion; Dark matter. 1. INTRODUCTION ence of a DM halo centered in the Sun and its influence upon the motion of planets; numerical simulations due to Diemand et al. [8] show the presence of DM clumps surviving near A 305-day Earth free precession was predicted by Euler in the solar circle; Adler [9] suggests that internal heat produc- the 18th century and was sought since then by astronomers in tion in Neptune and hot-Jupiter exoplanets is due to accretion the form of small latitude variations. F. Kustner¨ in 1888 and of planet-bound, not self-annihilating DM. Although the na- S. C. Chandler in 1891 detected such a motion but with a pe- ture of the particles that form DM is not known precisely (see riod of approximately 435 days.
    [Show full text]
  • Constraining Ceres' Interior from Its Rotational Motion
    A&A 535, A43 (2011) Astronomy DOI: 10.1051/0004-6361/201116563 & c ESO 2011 Astrophysics Constraining Ceres’ interior from its rotational motion N. Rambaux1,2, J. Castillo-Rogez3, V. Dehant4, and P. Kuchynka2,3 1 Université Pierre et Marie Curie, UPMC–Paris 06, France e-mail: [nicolas.rambaux;kuchynka]@imcce.fr 2 IMCCE, Observatoire de Paris, CNRS UMR 8028, 77 avenue Denfert-Rochereau, 75014 Paris, France 3 Jet Propulsion Laboratory, Caltech, Pasadena, USA e-mail: [email protected] 4 Royal Observatory of Belgium, 3 avenue Circulaire, 1180 Brussels, Belgium Received 24 January 2011 / Accepted 14 July 2011 ABSTRACT Context. Ceres is the most massive body of the asteroid belt and contains about 25 wt.% (weight percent) of water. Understanding its thermal evolution and assessing its current state are major goals of the Dawn mission. Constraints on its internal structure can be inferred from various types of observations. In particular, detailed knowledge of the rotational motion can help constrain the mass distribution inside the body, which in turn can lead to information about its geophysical history. Aims. We investigate the signature of internal processes on Ceres rotational motion and discuss future measurements that can possibly be performed by the spacecraft Dawn and will help to constrain Ceres’ internal structure. Methods. We compute the polar motion, precession-nutation, and length-of-day variations. We estimate the amplitudes of the rigid and non-rigid responses for these various motions for models of Ceres’ interior constrained by shape data and surface properties. Results. As a general result, the amplitudes of oscillations in the rotation appear to be small, and their determination from spaceborne techniques will be challenging.
    [Show full text]
  • Present True Polar Wander in the Frame of the Geotectonic Reference System
    1661-8726/08/030629-8 Swiss J. Geosci. 101 (2008) 629–636 DOI 10.1007/s00015-008-1284-y Birkhäuser Verlag, Basel, 2008 Present true polar wander in the frame of the Geotectonic Reference System NAZARIO PAVONI Key words: Geotectonic Reference System, polar wander, geodynamics, geotectonic bipolarity ABSTRACT The Mesozoic-Cenozoic evolution of the Earth’s lithosphere reveals a funda- mA which are responsible for the two geoid highs results in the long-standing mental hemispherical symmetry inherent in global tectonics. The symmetry stability of location of the geotectonic axis PA. The Earth’s rotation axis is is documented by the concurrent regular growth of the Pacific and African oriented perpendicularly to the PA axis. Owing to the extraordinary stabil- plates over the past 180 million years, and by the antipodal position of the two ity of the geotectonic axis, any change of orientation of the rotation axis, e.g. plates. The plates are centered on the equator, where center P of the Pacific induced by post-glacial rebound, occurs in such a way that the axis remains plate is located at 170° W/0° N, and center A of the African plate at 10° E/0° N. in the equatorial plane of the geotectonic system, i.e. in the 80° W/100° E P and A define a system of spherical coordinates, the Geotectonic Reference meridional plane. Observed present polar wander is directed towards 80° W System GRS, which shows a distinct relation to Cenozoic global tectonics. P (79.2 ± 0.2° W). This indicates that the present true polar wander is directed and A mark the poles of the geotectonic axis PA.
    [Show full text]
  • Excitation and Damping of the Chandler Wobble the Spinning
    Excitation and damping of the Chandler Wobble The spinning Earth is driven into what is called its free Eulerian nutation or, geophysically, its Chandler wobble by redistributions of mass within the Earth and/or by externally applied shocks. Walter Monk in the 1960s suggested that as earthquakes redistribute lithospheric mass, it may be that one could recognize the moments of earthquakes in the record of the Chandler wobble. Mansinha and Smylie in 1968 suggested that as great earthquakes probably accumulate a redistribution of mass even prior to fracture, it might be possible to predict the times of megathrust events through careful examination of the rotation pole path. Smylie, Clarke and Mansinha1 (1970) sought to recognize perturbations in the rotation pole path which might be ascribed to earthquakes. They used a classical time-series technique called "deconvolution" that had been so successfully applied in seismic petroleum surveying in the previous decade. While there is no real doubt that earthquakes could and should contribute to episodic excitation of the Chandler wobble and so to variations in the momentary rotation pole path, most geodesists doubt that any clearly demonstrated excitation by earthquakes has been seen. Now, as pole-path measurements are good to within a millimetre or two, one might expect that if a significant contribution to the wobble and pole path is due to earthquakes, we should be able to recognize it. Doug Smylie has continued to research this effect until today. In 1987, Lalu Mansinha and I2 looked into the problem by employing what we argued was a better statistical model for the excitation and hence claimed a better deconvolution method for the recognition of earthquake-driven pole- path steps.
    [Show full text]
  • The Ocean Pole Tide: a Review
    Executive Committee Program Committee Fig 1. Attendee Profile by Research Interest Yun-Tai CHEN David HIGGITT, Chair Institute of Geophysics, The University of Nottingham China Earthquake Administration SE 19% Ningbo China AS 23% The Ocean Pole Tide: A ReviewBenjamin Fong CHAO Tetsuo NAKAZAWA, AS Section Institute of Earth Sciences, BG 2% Korea Meteorological Administration Academia Sinica ST 16% HS 12% Wendy WANG, BG Section David HIGGITT College of Global Change and Earth The University of Notthingham, System Science, Beijing Normal University Ningbo China Richard Gross PS 10% IG 8% Kun-Yeun HAN, HS Section Adam SWITZER OS 10% Kyungpook National University Earth Observatory of Singapore Atmospheric Sciences (AS) Biogeosciences (BG) James GOFF, IG Section Hydrological Sciences (HS) Interdisciplinary Geosciences (IG) University of New South Wales Jet Propulsion Laboratory Ocean Sciences (OS) Planetary Sciences (PS) Robin ROBERTSON, OS Section Solar & Terrestrial Sciences (ST) Solid Earth Sciences (SE) University of New South Wales at the Australian Defense Force Academy California Institute of Technology Fig 2. Representation by Country/Region Noriyuki NAMIKI, PS Section National Astronomical Observatory of Pasadena, CA 91109–8099, USA Japan Nanan BALAN, ST Section National Institute for Space Research (Instituto Nacional de Pesquisas Espaciais- Asia Oceania Geosciences Society INPE) th 13 Annual Meeting Hai Thanh TRAN, SE Section Hanoi University of Mining and Geology Partners & Supporters of AOGS July 31 to August 5, 2016 Beijing, China
    [Show full text]
  • Chandler Wobble: Two More Large Phase Jumps Revealed
    LETTER Earth Planets Space, 62, 943–947, 2010 Chandler wobble: two more large phase jumps revealed Zinovy Malkin and Natalia Miller Pulkovo Observatory, Pulkovskoe Ch. 65, St. Petersburg 196140, Russia (Received August 23, 2009; Accepted November 8, 2010; Online published February 3, 2011) Investigations of the anomalies in the Earth rotation, in particular, the polar motion components, play an important role in our understanding of the processes that drive changes in the Earth’s surface, interior, atmosphere, and ocean. This paper is primarily aimed at investigation of the Chandler wobble (CW) at the whole available 163-year interval to search for the major CW amplitude and phase variations. First, the CW signal was extracted from the IERS (International Earth Rotation and Reference Systems Service) Pole coordinates time series using two digital filters: the singular spectrum analysis and Fourier transform. The CW amplitude and phase variations were examined by means of the wavelet transform and Hilbert transform. Results of our analysis have shown that, besides the well-known CW phase jump in the 1920s, two other large phase jumps have been found in the 1850s and 2000s. As in the 1920s, these phase jumps occurred contemporarily with a sharp decrease in the CW amplitude. Key words: Earth rotation, polar motion, Chandler wobble, amplitude and phase variations, phase jumps. 1. Introduction IERS (International Earth Rotation and Reference Systems The Chandler wobble (CW) is one of the main compo- Service) C01 PM time series (Miller, 2008) has shown clear nents of motion of the Earth’s rotation axis relative to the evidence of two other large CW phase jumps that occurred Earth’s surface, also called Polar motion (PM).
    [Show full text]
  • A Review of Studies Made on the Decade Fluctuations in the Earth's Rate of Rotation
    a.^lillUUIUJ Hal bureaJ Admin. Bldg. py, E-01 KOVa^^ST ^ ; I 358 A Review of Studies liAade on tlie Decade Fluctuations in the Eartli's Rate of Rotation o' Kf.*^ c. ,/' U.S. DEPARTMENT OF COMMERCE z National Bureau of Standards p. \ 'n * *''»eAU o« : I THE NATIONAL BUREAU OF STANDARDS The National Bureau of Standards^ provides measurement and technical information service essential to the efficiency and effectiveness of the work of the Nation's scientists and engineers. Thi1 Bureau serves also as a focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To accomplish this mission, the Bureau is organized into three institutes covering broad program areas ofl research and services: THE INSTITUTE FOR BASIC STANDARDS . provides the central basis within the United States for a complete and consistent system of physical measurements, coordinates that system with the measurement systems of other nations, and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. This Institute comprises a series of divisions, each serving a classical subject matter area: —Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic Physics—Physic Chemistry—Radiation Physics—Laboratory Astrophysics^—Radio Standards Laboratory,^ which includes Radio Standards Physics and Radio Standards Engineering—Office of Standard Refer- ence Data. THE INSTITUTE FOR MATERIALS RESEARCH . conducts materials research and provides associated materials services including mainly reference materials and data on the properties of ma^ terials. Beyond its direct interest to the Nation's scientists and engineers, this Institute yields services which are essential to the advancement of technology in industry and commerce.
    [Show full text]