Current horizontal strain field in Chinese mainland derived from GPS data

Abstract

The current crustal horizontal strain field is given in the paper based on the horizontal movement rates obtained from about 400 GPS stations located in Chinese mainland and its surrounding areas. The results show: a) The horizontal strain in Chinese mainland is "strong in the west and weak in the east" and the shear strain is larger than the normal strain (absolute magnitude). The general strain magnitude is 10-S/a and in local regions is 10-7/a, but the strain distribution is not homogeneous; b) The regions with the most significant NS-trending strains are the Himalayas belt along the western segment of Chinese southern boundary, the segment of 36°N-42°N along the western boundary and the northem margin of Qaidam block; c) The EW-trending strain variation along the western margin is the maximum and it is characterized by the alternatively positive and negative variations from the west to the east; d) The regions with larger magnitudes OfREN (NE-trending shear strain) and Rm~ (maximum shear strain) are Himalayas belt, the segment of 36°N--42°N along the western boundary, the western part of Qaidam block, Sichuan-Yunnan (Chuan-Dian) rhombic block and the border area of Alxa, Qilian and Tarim blocks; e) The surrounding area of Qinghai-Xizang (Qingzang) block is mainly superfacial contraction and its interior is basically superfacial expansion. The area to its north is mainly superfacial contraction with the maximum magnitude along the westem boundary and the minimum magnitude in the eastern part (except Yanshan tectonic zone); f) In the west of the western part, the principal compressive strain is in the SN direction and the principal tensile strain is in the EW direction, while in the eastem margin area of the westem part, the principal compressive strain is proximate EW and the principal tensile strain is about SN. The principal strain direction of Chuan-Dian rhombic block has changed greatly. In the northern part, it is compression in the EW and tension in the SN, while in the southern part, it is just the opposite; g) The strain pattern in Chinese mainland might be the integration of "block mode" and "successive deformation mode". In addition, the shear strain might be the small-scale dominant strain. Such a result might be resulted from the collision of Indian plate and the boundaries coupling, and it is also closely related to the motion of deep-seated matters and the physical nature of crustal medium. Therefore, it should be noted that since the GPS stations are not homogenous in spatial distribution, the obtained strain fields and the scales of the strain should be different.

Estimation of GPS strain rate and its error analysis in the Chinese continent

“…Many workers in the world (e.g., Kato et al, 1998;Calais et al, 2000;Holt et al, 2000;Henry et al, 2001;Savage et al, 2001;Bennett et al, 2003;Mazzotti et al, 2005;Allmendinger et al, 2007) studied how to calculate geo-strain from GPS velocities. At the same time, Chinese scientists try to calculate the geo-strain rate in the Chinese continent by means of many methods (e.g., Gu et al, 2001;Yang et al, 2002Yang et al, , 2005Shen et al, 2003;Jiang et al, 2003;Huang and Wang, 2003;Zhu et al, 2006;Gan et al, 2007). There is no doubt that their work gives varied approaches to obtain the strain rate field from GPS data.…”

Geothermic activity and seismotectonics in the altitude of the Tibetan plateau

“…The extensional strain ratio is 20×10 −9 /a, which is the greatest one in the Chinese mainland (Yang et al, 2002). Results of resistivity show the thermal lithosphere is about 120 km in the zone northwest of Lhasa in the south plateau.…”

Compressive tectonics around Tibetan plateau edges

“…Figure 5 shows the horizontal displacement vector rate surveyed by GPS in the Tibetan plateau and its surroundings (Yang et al, 2002). It can be seen that great displacement vectors toward the north or NNE directions distribute along the Himalaya Mountains and the southern edge of the Tibetan plateau.…”