IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS014 Poster presentation 2279
Antarctic plate boundary with the gravimetric tomography data
Dr. Rudolf Greku
IASPEI IASPEI
Deep structure of the Antarctic plate boundary is obtained from surface up to the core for the space of
40,000 km using the gravimetric tomography method [1]. Coordinates of the boundary is used from [2].
This boundary is as contact zone with segments of other five large plates (Africa, Australia, Nazca,
Pacific, South America) and four small plates (Shetland, Scotia, Sandwich, Somalia). It is obvious that
the historical nature and tectonics of these plates are different for both the lithosphere and mantle
layers. The structure shows a distribution of density inhomogeneities calculated as anomalies relatively
the PREM density model using harmonic coefficients of the EGM96 global geoid model. Space resolution
of the boundary vertical cross-section is of 60 km, radial resolutions on the image are different to show
important features within distinct layers: solid surface-20 km, 20km-100km, 100km-750km, 750km-
5300km. Data of the bottom topography (ETOPO5, NOAA-NGDC), free-air gravity anomalies [KMS2002,
3], and depths of Moho from the crustal model [Crust 2.0, 4] accompany our tomographic model.
Several cross sections which are orthogonal to the boundary are calculated also to observe a structure
and interaction of adjacent plates within the borderland and triple-junction points that are common to
all segments. In the mantle dominate two bodies (plumes) with maximum depths near of 2800 km on
the core-mantle boundary. Less dense masses which ascend from the Ross Sea plum become as three
branches from depth of 200 km to the Australian-Antarctic Discordance (AAD, 124E), Ross Sea (175E)
and to the boundary of the Nazca plate (100W). Dense masses descend from surface like subduction
slabes and concentrate at depth of 60 km and 280 km. We discover a new information in area of the
AAD structure where thinning hoter masses penetrate into the colder crust and lithosphere. Something
similar to that is at the Nazca boundary. Gravimetric tomography data for the AAD area exhibit more
detailed structure in comparison with the seismic tomography [5]. 1. Greku R.Kh., Kulikov A.A., Greku
T.R., Earths structure with the gravimetric tomography method, this XXIV IUGG 2007, JSS011. 2. Bird
P., An updated digital model of plate boundaries, An Electronic Journ. of the Earth Sci., Volume 4,
Number 3, 14 March 2003, 10.1029/2001GC000252. 3. Andersen O.B., Dreyer S., Knudsen P, Berry
P.A.M., Mathers E. L., Trimmer R., Kenyon S., Deriving 2Hz ERS-1 geodetic mission altimetry for gravity
and marine geoid proposes, www.research.dk/GRAVITY. 4. Bassin, C., Laske, G. and Masters, G., The
Current Limits of Resolution for Surface Wave Tomography in North America, EOS Trans AGU, 81, F897,
2000. 5. Ritzwoller M.H., Shapiro N.M., Levshin A.L., Leahy G.M., 2001, J. Geophys. Res., 106, 30645.
Keywords: tomography, boundary, antarctica