Extensional basins include mainly grabens and half grabens displaced along a lower detachment. Based on area balance theory, there is a linear relationship between a height of regional and the lower detachment h on the outside of the basin and “lost area S ” from the regional in the basin. The pre-growth beds above lower detachment are of the same extensional displacement so that an “ S-h diagram” can be used to determine the depth to lower detachment and to calculate the total extensional displacement of the beds above the lower detachment. The extensional displacement is dominated by the heave of various scale normal faults. The displacement of obvious faults can be immediately figured out from the measured bed-length. The requisite extension calculated by area balance is the layer-parallel strain, which could be accommodated by displacement on sub-resolution faults. Accordingly, the layer-parallel strain can help us predict the magnitude and distribution of sub-resolution faults on the basis of analysis of the structural style and rheological behavior. Based on area balance theory, there is a linear relationship between a height of regional and the lower detachment h on the outside of the basin and “lost area S ” from the regional in the basin. The pre-growth beds above lower detachment are of the same extensional displacement so that an “Sh diagram ” can be used to determine the depth to lower detachment and to calculate the total extensional displacement of the bed above the lower detachment. The extensional displacement is dominated by the heave of various scale normal faults. The displacement of obvious faults can be immediately figured out from the measured bed-length. The requisite extension calculated by area balance is the layer-parallel strain, which could be accommodated by displacement on sub-resolution faults. Thus, the layer-parallel strain can help us predict the magnitude and distribution of sub-resolution fa ults on the basis of analysis of the structural style and rheological behavior.