Chart IV – Arrival times of P, X, C and R pulses: Supplement 4 from "Ground vibrations near explosions" (Thesis)

Records are shown of the three components of ground vibration taken at distances out to 3284 meters following small explosions of dynamite about ten meters underground. The apparatus used to record this motion is described, and its limitations discussed. The refracted compressional waves recorded are used to calculate roughly the thickness of the near surface layers. Three principal dispersed waves are recognized and described. It is shown that two of these do not behave like any well known type of wave motion. It is pointed out that this is not surprising since the near surface material is probably neither homogeneous nor elastic and these conditions are required by the classical theories. The third dispersed wave is shown to closely resemble a modified Rayleigh wave. Three published theories of such modified motion are reviewed and compared with the observations. The recorded data are also compared with other similar records copies of which have been published