Geoscience Reference
In-Depth Information
Figure 5.2 Topographic relief (colored background), faults (orange lines), and seismicity (dots for
epicenters) for North China. Blue dots: historic earthquakes; red dots: instrumentally recorded earth-
quakes. For color version, see Plates section.
Cenozoic. Today, these regions are marked by flat, low-elevation (
50-200 m) and thin
lithosphere (
60 km in places), and the upper crust includes thick Quaternary sediments
covering widespread extensional basins. The fault systems are complex and widespread.
The boundary between the North China Plain and the coastal regions is the northeast-
trending Tanlu fault (
Figure 5.2
)
, a major strike-slip fault system developed during the
Mesozoic collision between the North and South China blocks, but with little slip through
The southern boundary of the North China Block is the east-trending, late Triassic
Qinling-Dabie orogenic belt created by the collision between the North and South China
blocks (
Figure 5.2
)
; the northern boundary is the Hetao rift valley along the northern rim
of the Ordos Plateau, and the Yanshan-Yinshan mountain belts further to the east. Along
the southwestern margin of the North China Block, the Ordos Plateau encounters the
northeastern corner of the laterally expanding Tibetan Plateau, forming a fold-and-thrust
belt in the late Cenozoic.
The topographic boundary between the high-standing western part of the North China
Block and the low-altitude North China Plain is abrupt along the eastern flank of the
Taihangshan mountain ranges
(
Figure 5.2
)
. This boundary is also marked by the largest
gradients of gravity in east Asia, corresponding to large gradients of crustal and litho-
coastal regions is characterized by low seismic velocity structures, which may be related
