中国西部地区门源—平凉—渭南地震测深剖面资料的分析解释

本文所处理的地震测深剖面资料,是一条途经陕、甘、宁、青四省,由7个炮点和12个记录分支组成的、全长约970km的地壳折射资料。 本文通过走时反演、射线追踪和合成地震图等分析解释手段,给出各分支的结构参数和全测线的横向变化。整个地壳大体分四层,其参数为 H1=3.32±1.01 km,V1=4.35±0.79 km; H2=11.79±2.77 km,V2=6.06±0.24 km; H3=11.58±4.32 km,V3=6.35±0.26 km; H4=17.64±7.25 km,V4=6.52±0.57 km. 地壳总厚度为45.60±11.01km.莫氏面自西向东逐渐变浅,在西段较为平缓,在中段和东段起伏较大,似乎显示出一个上端略宽、下端略窄的“U”形构造.这种构造有助于说明该区的大地构造特点和地震孕育的深部条件.

AN INTERPRETATION OF THE DSS DATA ON MENYUAN-PINGLING-WEINAN PROFILE IN WEST CHINA

In order to study the deep structure in West China,a profile of deep seismic sounding （DSS） has been made by the State Seismologieal Bureau （SSB）. This profile starts from Menyuan （门源） at its west end and to Weinan （渭南） at its east end. Total length is about 970 km.On the profile are 7 shooting points,constituting a continuous profiling of forward and reverse shooting. Based on kinematic and dynamic characteristics of waves,we can recognize a head wave from crystalling basement and three reflected waves from M-discontinuty and others. We have used several methods of interpretation,such as inversion by travel times,ray tracing and synthetic seismograms. We can divided the crust into four layers with the following structure parameters:H1= 03.32±1.01 km,V1 = 4.35±0.79 km/sec;H2 = 11.79±2.77 km,V2 = 6.06±0.24km/sec;H3 = 11.58±4.32 km,V3 = 6.35±0.26 km/sec;H4 = 17.64±7.25 km,V4 = 6.52±0.57 km/sec.The average thickness of the crust is 45.60±11.01 km.The results indicated that the crust in this region is laterally inhomogeous. The relieves of M-boundaries of the,west part of the profile are comparatively small,while those of the middle and east parts are larger. They seem to show a U-shaped structure which is wider in the upper part,and this is favouable to explain the geological tectonics and earthquake generation in this region.