In mathematics the solution to an inverse problem has come to mean
the ``determination'' of material properties from wavefields.
Often this is achieved with a ``convergent sequence.''
Geophysicists are less precise (or more inclusive) about what they mean
by ``determination.''
In some chapters of this book reflectors are ``determined''
by the exploding-reflection concept.
In chapter shot-to-geophone offset is incorporated,
and reflectivity *c*(*x*,*z*) and velocity *v*(*z*) are ``determined''
with a buried-experiment concept.
In chapter the concept is developed of suppressing
multiple reflections and finding the ``true'' amplitudes of
reflections by having the upcoming wave
vanish before the onset of the downgoing wave.
Other imaging concepts seem likely to result from future processing schemes.
It might be possible to show that some of our ``determinations'' coincide
with those of mathematicians,
but such coincidence is not our goal here.
Such a goal is formulated more directly in my third book .

10/31/1997