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 2320
Folding of MOHO beneath Tibet and South Korea
Dr. Young Hong Shin
Space Geodesy Korea Astronomy & Space Science Institute IASPEI
Houze Xu, Pil Ho Park, Jong Uk Park, Jeong Ho Baek
We present the folding structures of Moho beneath the Tibetan Plateau and the southern part of the
Korean Peninsula, which show good coincidence with observations from modern global positioning
system (GPS). The Tibetan Plateau is greatly affected by heavy compression between Eurasian and
Indian Plates. The Korean Peninsula is closely located to the collisional boundary between Eurasian,
Pacific, and Philippine Plates, resulting in a compressional force. Thus the study areas possibly have
particular deformation structures related with the tectonic environment. Our Moho folding model is
based on the gravimetric Moho undulation model and the flexural isostasy model. To estimate the
deformation of the Tibetan Moho, we use the recent GRACE satellite-based gravity model, GGM02C as
the principle gravity data. Finding out some defects of the former method in estimating the prevailing
wavelengths of the folding structure, we suggest a new method producing different results. Our Moho
folding model shows: (a) EW directional trend is prominent in western Tibet, while NS directional one in
eastern Tibet, (b) the folding structures are not limited to the inside of the plateau but extended to the
near surroundings of the plateau, (c) the amplitude of the folding is about 7.5km inside the plateau, (d)
rapid decreasing of the amplitude is observed outside the plateau, (e) the intervals between the folding
troughs are observed to keep a semi-constant distance of about 330-340km, which is quite smaller than
that of the previous study of about 500~700km, and (f) our results are in good agreement with the
modern GPS measurements and relate with weakness and partial melting of the Tibetan lithosphere. In
examining the southern part of the Korean Peninsula, we use surface gravity data as the principle data.
Our model of the Moho deformation shows: (a) the Moho folding structure is parallel to SKTL (South
Korean Tectonic Line), which indicates a positive association with the collision of the Yeongnam and
Gyeonggi Massifs and a repeated compression afterwards, (b) the amplitude of the folding is about
1.5km and wavelength about 150-200km, (c) the Moho beneath the Gyeongsang Basin has remarkably
risen; this seems to result from both collisional compression and buoyancy caused by magmatic
underplating, (d) the Moho deformation is the shallowest east of the Taebaek Mountains and deepens
toward the west direction, which can be interpreted as the results of opening of East Sea (Japan Sea)
and Ulleung Basin. The Moho deformation model in this area correlates well with earthquake distribution
and crustal movement measured by GPS. The observed prevailing wavelengths of the folding structures
of the two areas are compatible with predicted ones of elastic plates
Keywords: folding, moho, tectonics