The specialty of seismic imaging in foothill area originates from the complex surface conditions,which leads to low S/N and
serious moveout between gathers.Because of the rugged topography and near-surface lateral velocity variation,the conventional
root-mean-square velocity analysis based on CMP gathers stacking is no longer effective.Up to now,there does not exist an
effective imaging processing procedure widely accepted for foothill seismic data.After analyzing the seismic wave propagation
and the limitation of conventional processing methods,we proposed a new imaging workflow.The workflow includes three key
steps:①choosing a smoothed datum as close to the topography to remove the high wavenumber moveout.The prestack depth
migration and velocity model building are also based on the datum;②Kirchhoff PSDM based Monta Carlo velocity inversion is
used to estimate the background and smoothed initial velocity.③beam ray PSDM based velocity tomography in angle domain
is used to estimate the more fine and accurate migration velocity.In addition,the in-phase stacking the reflections from half
Fresnel band is used to do the noise attenuation,which is very important for the effective migration velocity estimation and
velocity model building.The near-surface velocity model building replaces the so-called static correction.The basic numerical
tests demonstrate the effectiveness of this procedure.
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