| Although a hammer method was used as a shear sound source, the axial resolution (about 0.5m) was difficult to improve. Therefore, to improve the axial resolution, we newly introduce a shear sound source using super-magnetstriction vibrator and pulse compression method. From the simulation results, when Δf(the difference between start and stop frequency) is more than 700Hz, the axial resolution become under 0.2m. To confirm this result, exploration experiments are carried out. From the experimental results, we confirmed that the validity of the pulse compression method for resolution improvement of underground image. |