Abstract:

        The Qiongdongnan basin  is an extensional basin  formed  in Late- Eocene.  In  this study, based on  the  flexure  isostasy
principle  and flexural cantilever model， we utilize 2D structurcal simulation software and calculate the effective elastic thickness
valuse (Te) and the extensional factors on 2D interpreted seismic profiles. The results show that the effective elastic thicknesses
vary  in  the  range of 1-5 km, and  their optimum value  is 3 km. The extensional  factors change between 1.3 and 1.5, about 1.5
for the post-rift period with forward modeling, and about 1.3 for the syn-rift period with inverse modeling. Finally, we discuss the
possible influential factors of the activity of the Red River fault in the Cenozoic and the South China Sea spreading.

Key words: Qiongdongnan basin, effective elastic thickness, stretch factor, Red River fault, modeling of lithospheric structure