Multiple phases analysis of deep seismic sounding records in North China Craton

The North China Craton (NCC) is a key region to study the destruction of the ancient craton. Two groups of phases (denoted as “Pw1” and “Pw2”), which are parallel to the PmP phase reflected from the Moho discontinuity and the PLP phase reflected from the Lithosphere and Asthenosphere Boundary(LAB) respectively, are found on the record section of the Rongcheng-Xinzhou-Alxa long-range deep seismic sounding profile. The nature of the two phases is still unclear, although they are clearly observable and reverberant. In this paper, we use travel time inversion and amplitude forward modelling to fit the reflected and refracted phases in the lithosphere. The results show: (1) the Pw1 is a multiple reflected phase which is successively reflected by the crystalline basement, the surface, the Moho and then finally received on the surface; (2) the Pw2 phase is also a multiple reflected phase successively reflected by the crystalline basement, the surface, the LAB interface and then received on the surface. We conclude that the significant velocity difference between the thick sedimentary cover and the crystalline basement in the North China rifted basin may be the main reason for generating the multiple reflections. Furthermore, the two multiple reflections provide potent constraints on the lithospheric velocity model, and constitute seismological evidence for the lithospheric thinning in the eastern NCC.