Airborne geophysical data were used to analyze the complex structures of
eastern Thailand. For visual interpretation, the magnetic data were enhanced
by the analytical signal, and we used reduction to the pole (RTP)
and vertical derivative (VD) grid methods, while the radiometric data were
enhanced by false-colored composites and rectification. The main regional
structure of this area trends roughly in northwest-southeast direction, with
sinistral faulting movements. These are the result of compression tectonics
(v1 in an east-west direction) that generated strike-slip movement during
the pre Indian-Asian collision. These faults are cross-cut by the northeastsouthwest-running
sinistral fault and the northwest-southeast dextral fault,
which occurred following the Indian-Asian collision, from the transpession
sinistral shear in the northwest-southeast direction. Three distinct geophysical
domains are discernible; the Northern, Central and Southern Domains.
These three domains correspond very well with the established
geotectonic units, as the Northern Domain with the Indochina block, the
Central Domain with the Nakhonthai block, the Upper Southern Sub-domain
with the Lampang-Chaing Rai block, and the Lower Southern Subdomain
with the Shan Thai block. The Indochina block is a single unit with
moderate radiometric intensities and a high magnetic signature. The direction
of the east-west lineament pattern is underlain by Mesozoic nonmarine
sedimentary rock, with mafic igneous bodies beneath this. The
Nakhonthai block has a strong magnetic signature and a very weak radiometric
intensity, with Late Paleozoic-Early Mesozoic volcanic rock and
mélange zones that are largely covered by Cenozoic sediments. The boundaries
of this block are the southern extension of the Mae Ping Faults and are
oriented in the northwest-southeast direction. The Lampang-Chaing Rai
and Shan Thai blocks, with very weak to moderate magnetic signatures and
moderate to very strong radiometric intensities are dominated by marine
clastic and igneous rocks or a northwest-southeast trending deformation
zone of inferred Precambrian complexes, respectively. It is suggested that
these tectonic plates collided against one another in a west-east direction