The tomographic estimation of seismic velocities from reflected raypaths
, by William S. Harlan
To estimate seismic transmission velocities from traveltimes along reflected raypaths,
one must first determine the positions of reflection points. The traveltimes between
sources and receives, if not picked directly from the data, are sufficiently constrained
by picked stacking velocities and zero-offset traveltimes. A particular velocity model
allows us to estimate reflection points which are most consistent with picked traveltimes
and their spatial derivatives at the surface. Perturbations of velocities along the
estimated raypaths can then minimize remaining errors in recorded traveltimes or stacking
velociteis. An improvement in the velocity model allows us iteratively to improve the
estimated reflection geometries.
STANFORD