f Improved traveltime tomography applied to cross-well seismic data

The main difficulty in geophysical traveltime tomography is the serious Jack of complete ray coverage due to the seismic experimental geometry. Many algebraic reconstruction algorithms in medical tomography have been applied to the straight-ray or curved-ray model in seismic experiments . A large number of modified algorithms concerned with cross-well tomography have been reported recently. The strategy is either to take full account of the experimental geometry in the discretization proce - dure, or to impose the geological constraints on the iteration procedure. However, these algebraic reconstruction techniques have been found to be very space and time-consuming on a computer with the large matrix manipulations .