Crustal structures of the Weihe graben and its surroundings from receiver functions

Abstract

We use 15 seismic stations, crossing the Qinling orogen (QO), Weihe graben (WG) and Ordos block (OB), to study the crustal structures by receiver functions (RFs) methods. The results show quite a difference in crustal structures and materials of three tectonic units (orogenic belt, extentional basin and stable craton). The average crustal thickness in the northern QO is 37.8 km, and Poisson ratio is 0.247, which indicates the increase of felsic materials in QO. In the southern OB, the average crustal thickness is 39.2 km and Poisson ratio is 0.265. Comparatively high value of Poisson ratio is related with old crystallized base in the lower crust and shallow sediments. The artificial RFs reveal that low-velocity and thick sediments have a significant effect on phases of the Mohorovicic discontinuity (Moho). As a result, the Moho phases in WG are tangled. S-wave velocity (VS) inversion shows that there are shallow sediment layers with 4-8 km’s thickness and high velocity zones in the middle-lower crust in WG. Complex Moho structure and high velocity zone may have been induced by the activities of the Weihe faults series.