Under certain highly simplified but realistic physical assumptions, the basic data from continuous velocity surveys in wells can be made to simulate the variations in acoustic impedance in the ground which give rise to seismic reflections. An electro-optical analog device is described which makes use of the basic well data to produce synthetic seismic records which resemble actual seismograms from shot hole explosions. This provides an interesting insight into the requisite physical conditions as well as the physical processes whereby seismic reflections are set up in the earth.