Focusing surface seismic signals to an image point is a key concept in seismic imaging. The resulting images are typically shown in two domains: time or depth. In this study, we use reverse-time modeling to demonstrate connections between the focused responses at the image points in both domains. We show that the kinematics (traveltimes) of the surface signals control the focusing position, whereas the dynamics (amplitudes) control the wavefield radiation direction after focusing. The focused responses in both domains can be related via the concept of image rays, which provide mapping between the two coordinate systems. Building on these observations, we show that the focusing operator that would lead to a focus (virtual source) at a specified location in time or depth domain can be expressed as deblurred time-reversed surface seismic signals (Green’s functions) from that point. Such an operator can be found solely from local event slopes measured directly from the common-midpoint (CMP) gathers without prior velocity knowledge. Slope information also allows us to specify the radiation direction perpendicular to the local structure after focusing. Therefore, the design of focusing operators at depth can be obtained from time-domain processing only.


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