The crustal structure of western Shandong and the high-velocity body in the crust

The crustal velocity structure of western Shandong is presented from a DSS profile with a length of 320 km.In this area,the depth of Moho layer is from 33 km to 35 km.The thickness of upper crust is 18～20 km,the velocity is 5.4～6.2 km/s; these of the lower crust are respectively 13～15 km,6.4～6.7 km/s.Pn velocity in this region is 7.9 km/s.Crustal velocity varies transversally at a rather large range.The mean velocity is from 6.2 km/s to 6.5 km/s,higher than the normal value.In the crust there are two nearly vertically high-velocity blocks,stretching from the lower crust to the upper crust reaching the bottom of the sediment basin.It is possible that a large mount of magma from the upper mantle gushes up into the crust,causing the increase of the crustal mean velocity.The high velocity blocks are the channels of mantle magma to go up through.