We address the problem of estimating seismic velocities inside the Earth which is necessary
for obtaining seismic images in regular Cartesian coordinates. The main goals are to
develop algorithms to convert time-migration velocities to true seismic velocities, and to
convert time-migrated images to depth images in regular Cartesian coordinates. Our main
results are three-fold. First, we establish a theoretical relation between the true seismic
velocities and the'time-migration velocities' using the paraxial ray tracing. Second, we …

We address the problem of estimating seismic velocities inside the earth which is necessary
for obtaining seismic images in regular Cartesian coordinates. We derive a relation between
the true seismic velocities and the routinely obtained so called” time migration velocities”,
which are some kind of mean velocities. We formulate an inverse problem and show that it is
ill-posed. We suggest three different approaches for solving it. We test these algorithms on
synthetic data and apply them to a field data example.