Current-day extending motion of Bohai Basin
渤海盆地的现今扩张运动

About extension of Bohai Basin, our predecessors obtained very researching results. But the principal direction, rate and range of the extension of Bohai Basin realized no up to know. In the paper, we will investigate these problems. On the basis of GPS surveying results from the Crustal Motion Observation Network of China, we created the velocity field relative to Eurasia Plate in Bohai Basin and its surrounding area. We divided the area into 8 blocks, and created the velocity models of these blocks, obtained the horizontal deformation velocity field and strain field in this area. By analyzing the space variation of the deformation velocity field and strain field, it is found that the Bohai and its surrounding area appears to be marked by NW-ward and SE-ward extending motion with extending rate of 2.5±1.8 mm/a. The extending ranges of NW-SE-ward and NE-SW-ward are at 310km and 410km respectively. The extending ranges of Bohai Basin are basically consistent with crust thinnest area of North China which indicates that extending deformations of upper crust are close relative with rise of upper mantle. The lithosphere thins and magma up-wills which lead to that the tensile deformation of upper crust occurred, it take the area of Bohai generate to a tensile basin.