斜向碰撞板塊前緣之下部岩圈動力流場側向變化

Taiwan orogeny has been interpreted in terms of
the “thin-skinned tectonics” model based on
observations of surface geology and shallow seismic
reflection profiles. It has been challenged that deep
process in the lithospheric depth might be actively
involved based on deep geophysical observations.
The potential involvement of dynamic flow of the
mantle lithosphere further complicates the
construction of a feasible theoretical model. In fact,
dynamic processes during plate collision have been a
research topic of great interest in recent years.
Conceptual models constructed to account for a suit of
geophysical observations that are otherwise
un-comprehensible based on geological models in
several noted collision zones have been devised. The
physics behind these models concern mainly the
Rayleigh-Taylor instability, or the more general
convective instability, if the thermal effect is
incorporated into the analysis of the instability,
occurring within the mantle lithosphere. It has been
shown that these types of lithospheric instability result
in various geophysical manifestations, including
seismogenic structure, S-wave anisotropy and seismic
velocity anomaly in the deep lithosphere. For the
Taiwan orogeny, there have already been documented
signatures of this type that demands the exploration of
how such lithosphere-wise process might be adopted
in the Taiwan tectonic region. We build the
three-dimensional, thermal-mechanical, numerical
modeling tool to explore the theoretical aspects of the
potential convective instability within the deep
Eurasia lithosphere, and the capability of consistently
interpreting geophysical observations. It is found
that due to the significant lateral variation of the rigors
of the plate collision within a wavelength of only a
few hundred kilometers form north to south,
convective instability within the relatively short
wavelength and timescale is not only very likely to
occur but also may serve as the critical transition in
between the two subduction systems to the north and
south that has flipping polarity. Our ultimate goal in
this study is to shed insights on the theoretical
framework of the Taiwan Orogeny and other orogeny
with similar oblique configurations.