Abstract：The displacement equation for horizontal axisymmetric deformation of aquifer，as a homogeneous and isotropic porous medium，is developed under assumptions that matrix material is perfectly elastic，that skeletal particles and water are homogeneous and are not compressible，and that changes of pore pressure in the aquifer lead only to horizontal displacements of the solid skeleton of the formation with constant vertical mechanical loading，but not to vertical displacements. Compared with the corresponding equations developed under traditional assumptions (Jacob assumptions)，the new equations have the same structural form but with a different coefficient. The new-defined displacement coefficient，though still constant，is greater than traditional one. The new equation should be distinguished from the traditional one unless the coefficients in them are obtained by field tests in the fields or model calibration. The calculation value of vertical compaction will be bigger than its actual value if the skeletal elastic water storage in the subsidence model is obtained from pumping test.
