ult and Zhouqu-liangdang fault.
Last century the crust velocity structure imagine were obtained using industrial explosion,
simultaneously high velocity structure was found in crust of Jingtai area, Gansu Province (Institute
of Geophysics, Chinese Academy of Sciences, 1981). The velocity structure along the
Maqên-Lanzhou-Jingbian deep seismic sounding (DSS) profile (LI et al, 2002 ) revealed that the
velocity structure are obvious different in different tectonic units, that is, crustal structure varied
from simple to very complex and number of layer increased from the northeast to the southwest.
The crust thickness is increased from 45 km to 60 km and average P-wave velocity is decreased
from 6.32 km/s to 6.0 km/s in the same direction as above. Crust layers, distribution of low velocity
and the property of reflection interface all are different greatly in two sides of Maqên fault
(A’nyêmaqên suture belt) where fault throw of Moho can reach to 4 km. Lower crust beneath the
south of Maqên fault has a strong reflection characteristics. There are two structure decouple belts
in the crust, one is brittle-ductile transition zone in middle crust, another is crust-mantle transition
zone. It is supposed that the activity of east Kunlun Bayan Har block is hierarchic in range of the
crust and reflects strong deformation of crust. The stromatolitheic structure with high-low velocity
interleave in lower crust of east Kunlun Bayan Har block may come from intrusion of upper man-
Figure 1 Geological map and location of seismic
station of Hongyuan-Barkam profile
1 Aba arc fault ;2 Hoh Sai Hu-Maqên fault ;
3 Wudang-diebu fault; 4 Zhouqu-liangdang
fault; 5 northern edge fault of Qinling earth’s
axis; 6 Riyueshan-Lajishan fault. The solid
triangles are location of seismic station
No.5 DUAN Yong-hong et al: CRUSTAL STRUCTURE USING RECEIVER FUNCTION 515
tle and ductile flow derived the layer sequence of high-low velocity interleave. The thickened
crust of the northeast part of Tibetan Plateau is mainly due to the thickened lower crust. The results
from Gonghe-Yushu DSS profile located in the east part of Qinghai Province in the
Sino-French joint project (Audrey et al, 2002) showed that the crust is thickening from the north
of the Kunlun fault to the Qiangtang block, the crust inner structure imagine and composition are
very different. The crust thickening to the north of Kunlun fault was due to upper crust thickening,
but to the south of Kunlun fault two layers crust thickening was due to original and thin crust beneath
Bayan Har covered over the lower crust. Because of two kinds of crust thickening mechanism
action simultaneously, terrain was lifted and local molten was not existed at the deep part of
crust. Beside above two DSS profiles, Menyuan-Pingliang-Weinan profile (WANG et al, 1995),
Lingtai-Amqog profile (MIN et al, 1991), Huashixia-Jianyang profile (CUI et al, 1996), Benzilan-
Tangke profile (WANG et al, 2003), Longmenshan triangle profile (CHENG et al, 1986) were
all crossed the studied area. The deep research results can sum up as below. 1 The features of
A’nyêmaqên suture belt and its west part, Kunlun fault, have been changed largely, converted from
lithosphere strike-slip fault to shear fault that subducted towards the north at medium angle and
the crust thickening took place in the low crust. 2 The crust and upper mantle structure varied
largely at the two sides of the A’nyêmaqên suture belt. 3 It is deduced that the block between
faults slipped toward the south or southeast in the late period of evolution of the
