Difference between pages "JSG T.29" and "JSG T.34"

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(Created page with "<big>'''JSG 0.16: Earth’s inner structure from combined geodetic and geophysical sources'''</big> Chairs: ''Robert Tenzer (China)''<br> Affiliation: ''Comm. 2 and 3'' __TO...")
 
(→‎Membership)
 
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<big>'''JSG 0.16: Earth’s inner structure from combined geodetic and geophysical sources'''</big>
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<big>'''JSG 0.21: Geophysical modelling of time variations in deformation and gravity'''</big>
  
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Chairs: ''Robert Tenzer (China)''<br>
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Chair: ''Yoshiyuki Tanaka (Japan)''<br>
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Affiliation: ''Comm. 2 and 3''
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Affiliation:''Comm. 2 and 3''
  
 
__TOC__
 
__TOC__
  
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===Introduction===
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===Terms of Reference===
  
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The satellite gravimetry missions, CHAllenging Mini-satellite Payload (CHAMP), the GRavity field and Climate Experiment (GRACE) and the Gravity field and steady-state Ocean Circulation Explorer (GOCE), significantly improved our knowledge on the external gravitational field of the Earth at the long-to-medium wavelengths (approximately up to a spherical harmonic degree of 250). Such improved information in terms of the accuracy and resolution has been utilized in studies of the Earth’s interior for a better understanding of the Earth’s inner structure and processes occurring within the lithosphere and sub-lithospheric mantle. Whereas the long-wavelength spectrum of the Earth’s gravitational field comprises mainly the signature of deep mantle density heterogeneities attributed to mantle convection, the medium wavelengths reflect the density structure of more shallow sources within the lithosphere. This allows studying and interpreting in more detail the gravitational features which are related to the global tectonism (including the oceanic subduction, orogenic formations, earthquakes, global lithospheric plate configuration, etc.), sub-lithospheric stresses, isostatic mechanisms, glacial isostatic adjustment, and other related geodynamic phenomena. Moreover, the Global Gravitational Models (GGMs) have been extensively used in studies of the lithospheric density structure and density interfaces such as for the gravimetric recovery of the Moho depth, lithospheric thickness as well as structure of sedimentary basins.
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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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Since the gravity observations could not be used alone to interpret the Earth’s inner density structure due to a non-uniqueness of inverse solutions (i.e. infinity many 3-D density structures could be attributed to the Earth’s gravity field), additional information is required to constrain the gravimetric methods for interpreting the Earth’s interior. These constraining data comprise primarily results of seismic surveys as well as additional geophysical, geothermal and geochemical parameters of the Earth. Moreover, numerous recent gravimetric studies of the Earth’s interior focus on the global and regional Moho recovery. The classical isostatic models (according to Airy and Pratt theories) are typically not able to model realistically the actual Moho geometry, due to the fact that the isostatic mass balance depends on loading and effective elastic thickness, rigidity, rheology of the lithosphere and viscosity of the asthenosphere. Moreover, geodynamic processes such as the glacial isostatic adjustment, present-day glacial melting, plate motion and mantle convection contribute to the time-dependent isostatic balance. To overcome these issues, processing strategies of combining gravity and seismic data (and possibly also additional constraining information) have to be applied to determine the actual Moho geometry.  
 
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The gravimetric methods applied in studies of the Earth’s inner density structure comprise - in principle - two categories. The methods for the gravimetric forward modeling are applied to model (and remove) the gravitational signature of known density structures in order to enhance the gravitational contribution of unknown (and sought) density structures and interfaces. The gravimetric inverse methods are then used to interpret these unknown density structures from the refined gravity data. It is obvious that the combination of gravity and seismic data (and other constraining information) is essential especially in solving the gravimetric inverse problems.  
 
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This gives us the platform and opportunities towards improving the theoretical and numerical methods applied in studies of Earth’s interior from multiple data sources, primarily focusing but not restricting only to combining gravimetric and seismic data. It is expected that the gravity data could improve our knowledge of the Earth’s interior over significant proportion of the world where seismic data are sparse or completely absent (such large parts of oceanic areas, Antarctica, Greenland and Africa). The gravity data could also provide additional information on the lithospheric structure and mechanisms, such as global tectonic configuration, geometry of subducted slabs, crustal thickening of orogenic formations and other phenomena.   
 
  
 
===Objectives===
 
===Objectives===
  
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* Development of the theoretical and numerical algorithms for combined processing of gravity, seismic and other types of geophysical data for a recovery of the Earth’s density structures and interfaces.
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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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* Development of fast numerical algorithms for combined data inversions.
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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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* Development of stochastic models for combined inversion including optimal weighting, regularization and spectral filtering.
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* Theoretical study to reveal the mechanisms of the individual processes.
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* Better understanding of uncertainties of interpreted results based on the error analysis of input data and applied numerical models. Geophysical and geodynamic clarification of results and their uncertainties.
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* Comparative study of theoretical methods using the existing codes.  
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* Recommendations for optimal data combinations, better understanding of possibilities and limiting factors associated with individual data types used for geophysical and geodynamic interpretations.
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* Forward and inverse modelling of deformation and gravity variations using observational data.
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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 web page with emphasis on exchange of ideas and recent progress, providing and updating bibliographic list of references of research results and relevant publications from different disciplines.
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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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* Work progress 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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* Possible collaboration between various geoscience study groups dealing with the modeling of the Earth’s interior and related scientific topics.  
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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.
  
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===Members===
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===Membership===
  
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'' '''Robert Tenzer (China), chair''' <br /> Lars Sjöberg (Sweden) <br /> Mohammad Bagherbandi (Sweden) <br /> Carla Braitenberg (Italy) <br /> Mehdi Eshagh (Sweden) <br /> Mirko Reguzzoni (Italy) <br /> Xiaodong Song (USA) <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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