Name : SUN,  Wenke
            Position : Associate Professor
            Division/Center :  Division of Monitoring and Computational Geoscience
            Research Area : Physical Geodesy, Geodynamics
 
 
 

Research :

    1.Determination of a high accuracy geoid by combining gravity missions and terrain gravity: Geoid is the special surface of equal
       gravitational potential close to sea level. Modern satellite positioning systems (such as GPS) measure point heights, which are
       related to a geometric surface - the ellipsoid. In order to transform ellipsoidal heights to topographic heights, the geoid undulations
       have to be subtracted. However, the geoid presently is known only to an accuracy of 1 m. To compete with the high GPS measurement
       accuracy (a cm-level), the geoid has to be known with the same accuracy. On the other hand, the geoid reflects the irregularities in
       the Earth's gravity field at the Earth's surface due to the inhomogeneous mass and density distribution in the Earth's interior. The
       new SST mission (such as CHAMP, GRACE or GOCE) derived global long-wave geoid will serve as an ideal basis for higher
       resolution global or regional gravity field modeling, and for a further refinement in regional and local areas. Therefore, as the first step,
       this research will analyze the three gravity missions (CHAMP, GRAVE and GOCE) to obtain a global high accuracy geoid. To
       determine a more refined geoid with an accuracy of 1cm, for a regional or a local area, the Stoke’s integral must be applied. To do
       that, many investigations should be done, such as, how to correctly consider the terrain correction? How to perform a downward
       continuation of gravity from terrain surface to the geoid? Et al.
    2.Co- and post-seismic deformations in a visco-elastic earth model: To study the slow deformations of the earth, such as those
       caused by a dislocation, post-glacial rebound, plate-plate interactions, and sea level variations, formulations and numerical
       calculations of visco-elastic Earth model is a basic theoretical work and must be carried out. The direct application of the
       visco-elastic theory is to study the co- and post-seismic deformations in a more realistic Earth model. We (Sun and Okubo) have
       successfully developed for the first time in the world an elastic dislocation theory for computing the co-seismic deformations
       (displacement, potential and gravity changes). The elastic dislocation theory is going to be extended into a visco-elastic one, which
       allows us to compute a time-dependent deformation.
    3.Deformations caused by an explosive source in a realistic earth model:  Deformations caused by an explosive source in a realistic earth
       model can serve as a basic reference for studying volcano, earthquake, and so on. This research will investigate the deformations
       (such as displacement, tilt, strain, potential and gravity changes) caused by an arbitrary explosive source buried in an arbitrary
       position in a spherically symmetric earth model. The impact of an explosive source on the time variation of the geoid is also to be
       considered. The researches can be done by a benefit of our previous dislocation theory.
 

Publications :

Sun, W. and L.E. Sjoberg, 2001. Permanent components of the crust, geoid and ocean depth tides, Journal of Geodynamics, 31, 323-339.

Sun, W. and L.E. Sjoberg, 2001. Tidal effects on determining a point at the bottom of the sea by combining GPS and Sonar observations, Marine Geodesy, 24, 35-51.

Sun, W. and L.E. Sjoberg, 2001. Convergence and optimal truncation of binomial expansions in isostatic compensations and terrain corrections, Journal of Geodesy, 74, 627-636.

Okubo, S., M. Furuya, W. Sun, Y. Tanaka, H. Watanabe, J. Oikawa, and T. Maekawa, September, 2000. Miyake-jima (Japan) Gravity and synthetic-aperture radar data; volcano through October 2000, Bulletin of the Global Volcanism Network, V.25, No.9, 8-11.

Sun, W. and L.E. Sjoberg, 2000. Tidal effects on determining a point at the bottom of the sea by combining GPS and Sonar observations, Report No. 1053, Department of Geodesy and Photogrammetry, Royal Institute of Technology, Stockholm, Sweden.

Sun, W. and L.E. Sjoberg, 1999. Gravitational potential changes of a spherically symmetric earth model caused by a surface load, Geophys. J. Int., 137, 449-468.

Sun, W. and L.E. Sjoberg, 1999. A new global topographic-isostatic model, Physics and Chemistry of the Earth, 24, 27-32.