Directivity of Phase Array Vibrators in Seismic Exploration

The extrusive difficulty in urban shallow strata seismic exploration with vibrators driven by electromagnetic force is that the weak reflective seismic signals are often flooded in strong background noise. For increasing signal‐noise ratio of seismic records, vibrator arrays can be used by phase controlling to concentrate seismic waves into a directed beam so as to enhance energy of seismic waves. We discuss the mechanism of wave beam forming for the phase array vibrators, give a definition of the marginal energy density for the seismic wave field, and make some quantitative analysis to the energy intensity along each direction on the snapshot of the wave field. Then the finite difference method is used to simulate the response to the Chirp signals produced by the phase array vibrators. When the concentration zone of the directed seismic beam is coincident with the range of the geophone arrangement, the energy intensity of the synthetic seismogram with the phase array vibrators is obviously higher than that with a single vibrator, and the uniformity of the amplitude of seismic wave for the phase array vibrators is obviously better than that for a set of vibrators sprung at the same time.