///This
    paper presents an implementation strategy of Kirchhoff integral prestack depth migration
    (PSDM) for large-scale seismic data sets, which is based on the 3D travel-time
    calculation method for arbitrary velocity variations. The strategy includes
    several key points: 1) common-offset data sets are the input data of the
    Kirchhoff PSDM algorithm; 2) one depth layer of image volume are resided in the
    inner memory, which thickness is dependent on the physics memory of the
    computer; and 3) the MPI plus OpenMp implementation strategy is proposed by
    taking consider of share memory and decreasing input and output (I/O) amount.
    All these points guarantee the balance of I/O and computation and make our
    Kirchhoff PSDM to be high efficient and accurate. The imaging results of the
    synthetic and real data demonstrate that the presented methods are correct and
    effective.