Difference between pages "JSG T.32" and "JSG T.34"

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<big>'''JSG 0.19: Time series analysis in geodesy'''</big>
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<big>'''JSG 0.21: Geophysical modelling of time variations in deformation and gravity'''</big>
  
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Chair: ''Wieslaw Kosek (Poland)''<br>
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Chair: ''Yoshiyuki Tanaka (Japan)''<br>
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Affiliation:''Comm. 3 and GGOS''
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Affiliation:''Comm. 2 and 3''
  
 
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===Terms of Reference===
 
===Terms of Reference===
  
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Observations of the space geodesy techniques and on the Earth's surface deliver a global picture of the Earth dynamics represented in the form of time series which describe 1) changes of the Earth surface geometry, 2) the fluctuations in the Earth orientation, and 3) the variations of the Earth’s gravitational field. The Earth's surface geometry, rotation and gravity field are the three components of the Global Geodetic Observing System (GGOS) which integrates them into one unique physical and mathematical model. However, temporal variations of these three components represent the total, integral effect of all global mass exchange between all elements of the Earth’s system including the Earth's interior and fluid layers:  atmosphere, ocean and land hydrology.
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In recent years, observational accuracy of ground-, satellite- and space-geodetic techniques has significantly improved which enables us to monitor temporal variations in surface deformations and gravity over various space and time scales. These variations are related to a wide range of surface and internal Earth’s processes, including the deformational response to glacial loading, solid earth and ocean tides, atmospheric and non-tidal ocean loadings, hydrological phenomena, earthquake and volcano activity, tsunamis from seismic to GIA-process frequencies. The interpretation of such high-accuracy observational data, more advanced theories are required in order to describe the individual processes and to quantify the individual signals in the geodetic data. To facilitate this, interactions between geophysical modelling and data modelling is mandatory.
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Different time series analysis methods have been applied to analyze all these geodetic time series for better understanding of the relations between all elements of the Earth’s system as well as their geophysical causes. The interactions between different components of the Earth’s system are very complex so the nature of considered signals in the geodetic time series is mostly wideband, irregular and non-stationary. Thus, it is recommended to apply wavelet based spectra-temporal analysis methods to analyze these geodetic time series as well as to explain their relations to geophysical processes in different frequency bands using time-frequency semblance and coherence methods. These spectra-temporal analysis methods and time-frequency semblance and coherence may be further developed to display reliably the features of the temporal or spatial variability of signals existing in various geodetic data, as well as in other source data sources.
 
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Geodetic time series include for example horizontal and vertical deformations of site positions determined from observations of space geodetic techniques. These site positions change due to e.g. plate tectonics, postglacial rebound, atmospheric, hydrology and ocean loading and earthquakes. However they are used to build the global international terrestrial reference frame (ITRF) which must be stable reference for all other geodetic observations including e.g. satellite orbit parameters and Earth's orientation parameters which consist of precession, nutation, polar motion and UT1-UTC that are necessary for transformation between the terrestrial and celestial reference frames. Geodetic time series include also temporal variations of Earth's gravity field where 1 arc-deg spherical harmonics correspond to the Earth’s centre of mass variations (long term mean of them determines the ITRF origin) and 2 degree spherical harmonics correspond to Earth rotation changes. Time series analysis methods can be also applied to analyze data on the Earth's surface including maps of the gravity field, sea level, ice covers, ionospheric total electron content and tropospheric delay as well as temporal variations of such surface data. The main problems to deal with include the estimation of deterministic (including trend and periodic variations) and stochastic (non-periodic variations and random changes) components of the geodetic time series as well as the application of digital filters for extracting specific components with a chosen frequency bandwidth.
 
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The multiple methods of time series analysis may be encouraged to be applied to the preprocessing of raw data from various geodetic measurements in order to promote the quality level of enhancement of signals existing in these data. The topic on the improvement of the edge effects in time series analysis may also be considered, since they may affect the reliability of long-range tendency (trends) estimated from data series as well as the real-time data processing and prediction.
 
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For coping with small geodetic samples one can apply simulation-based methods and if the data are sparse, Monte-Carlo simulation or bootstrap technique may be useful. Understanding the nature of geodetic time series is very important from the point of view of appropriate spectral analysis as well as application of filtering and prediction methods.
 
  
 
===Objectives===
 
===Objectives===
  
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* Study of the nature of geodetic time series to choose optimum time series analysis methods for filtering, spectral analysis, time frequency analysis and prediction.
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* Development of 1-D, 2-D, and 3-D elastic/anelastic Earth models for simulating the individual processes causing variations in deformation and gravity.
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* Study of Earth's geometry, rotation and gravity field variations and their geophysical causes in different frequency bands.
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* Development of phenomenological or dynamic theories to treat deformation and gravity variations which cannot be described by the above earth models (e.g., hydrology, cryosphere, poroelasticity) and consideration of such effects in the above earth models.
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* Evaluation of appropriate covariance matrices for the time series by applying the law of error propagation to the original measurements, including weighting schemes, regularization, etc.
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* Theoretical study to reveal the mechanisms of the individual processes.
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* Determination of the statistical significance levels of the results obtained by different time series analysis methods and algorithms applied to geodetic time series.
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* Comparative study of theoretical methods using the existing codes.  
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* Development and comparison of different time series analysis methods in order to point out their advantages and disadvantages.
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* Forward and inverse modelling of deformation and gravity variations using observational data.
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* Recommendations of different time series analysis methods for solving problems concerning specific geodetic time series.
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* Development of observational data analysis methods to extract the individual geophysical signals.
  
 
===Program of activities===
 
===Program of activities===
  
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* Launching of a website about time series analysis in geodesy providing list of papers from different disciplines as well as unification of terminology applied in time series analysis.
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* To launch an e-mail list to share information concerning research results and to interchange ideas for solving related problems.
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* Working meetings at the international symposia and presentation of research results at the appropriate sessions.
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* To open a web page to share publication lists and its update.
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* To hold an international workshop focusing on the above research theme.
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* To have sessions at international meetings (EGU, AGU, IAG, etc.) as needed.
  
 
===Membership===
 
===Membership===
  
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'' '''Wieslaw Kosek (Poland), chair''' <br /> Michael Schmidt (Germany) <br /> Jan Vondrák (Czech Republic) <br /> Waldemar Popinski (Poland) <br /> Tomasz Niedzielski (Poland) <br /> Johannes Boehm (Austria) <br /> Dawei Zheng (China) <br /> Yonghong Zhou (China) <br /> Mahmut O. Karslioglu (Turkey) <br /> Orhan Akyilmaz (Turkey) <br /> Laura Fernandez (Argentina) <br /> Richard Gross (USA) <br /> Olivier de Viron (France) <br /> Sergei Petrov (Russia) <br /> Michel Van Camp (Belgium) <br /> Hans Neuner (Germany) <br /> Xavier Collilieux (France) <br />''
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'' '''Yoshiyuki Tanaka (Japan), chair''' <br /> Zdeněk Martinec (Ireland) <br /> Erik Ivins (USA) <br /> Volker Klemann (Germany) <br /> Johannes Bouman (Germany) <br /> Jose Fernandez (Spain) <br /> Luce Fleitout (France) <br /> Pablo Jose Gonzales (UK) <br /> David Al-Attar (UK) <br /> Giorgio Spada (Italy) <br /> Gabriele Cambiotti (Italy) <br /> Peter Vajda (Slovak Republic) <br /> Wouter van der Wal (Netherlands) <br /> Riccardo Riva (Netherlands) <br /> Taco Broerse (Netherlands) <br /> Shin-Chan Han (Australia) <br /> Guangyu Fu (China) <br /> Benjamin Fong Chao (Taiwan) <br /> Jun'ichi Okuno (Japan) <br /> Masao Nakada (Japan) <br />''

Revision as of 14:20, 29 April 2016

JSG 0.21: Geophysical modelling of time variations in deformation and gravity

Chair: Yoshiyuki Tanaka (Japan)
Affiliation:Comm. 2 and 3

Terms of Reference

In recent years, observational accuracy of ground-, satellite- and space-geodetic techniques has significantly improved which enables us to monitor temporal variations in surface deformations and gravity over various space and time scales. These variations are related to a wide range of surface and internal Earth’s processes, including the deformational response to glacial loading, solid earth and ocean tides, atmospheric and non-tidal ocean loadings, hydrological phenomena, earthquake and volcano activity, tsunamis from seismic to GIA-process frequencies. The interpretation of such high-accuracy observational data, more advanced theories are required in order to describe the individual processes and to quantify the individual signals in the geodetic data. To facilitate this, interactions between geophysical modelling and data modelling is mandatory.

Objectives

  • Development of 1-D, 2-D, and 3-D elastic/anelastic Earth models for simulating the individual processes causing variations in deformation and gravity.
  • Development of phenomenological or dynamic theories to treat deformation and gravity variations which cannot be described by the above earth models (e.g., hydrology, cryosphere, poroelasticity) and consideration of such effects in the above earth models.
  • Theoretical study to reveal the mechanisms of the individual processes.
  • Comparative study of theoretical methods using the existing codes.
  • Forward and inverse modelling of deformation and gravity variations using observational data.
  • Development of observational data analysis methods to extract the individual geophysical signals.

Program of activities

  • To launch an e-mail list to share information concerning research results and to interchange ideas for solving related problems.
  • To open a web page to share publication lists and its update.
  • To hold an international workshop focusing on the above research theme.
  • To have sessions at international meetings (EGU, AGU, IAG, etc.) as needed.

Membership

Yoshiyuki Tanaka (Japan), chair
Zdeněk Martinec (Ireland)
Erik Ivins (USA)
Volker Klemann (Germany)
Johannes Bouman (Germany)
Jose Fernandez (Spain)
Luce Fleitout (France)
Pablo Jose Gonzales (UK)
David Al-Attar (UK)
Giorgio Spada (Italy)
Gabriele Cambiotti (Italy)
Peter Vajda (Slovak Republic)
Wouter van der Wal (Netherlands)
Riccardo Riva (Netherlands)
Taco Broerse (Netherlands)
Shin-Chan Han (Australia)
Guangyu Fu (China)
Benjamin Fong Chao (Taiwan)
Jun'ichi Okuno (Japan)
Masao Nakada (Japan)

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