Передача сейсмической энергии вглубь через стержень
статья в журнале
дата публикации: 1997
To solve many problems of prospecting and detailed study of the West-Siberian petroleum deposits, it is necessary to have a seismic reflection signal in the form of a single impulse, i.e. its amplitude spectrum must be constant in the frequency interval from 6-10 to 100-120 Hz. In West Siberia the grounds are mostly marshy, and to obtain the good quality seismograms, the reception of waves must be performed under the peat layer, while the excitation must be made by means of vertical grouping of sources situated at depths of 30-40 m. The last operation is suggested to be carried out using a rod vibrator, the radiating tip of which penetrates into the ground due to vibration and the static force. The increased attenuation of seismic waves at frequencies exceeding 50 Hz is compensated by a resonant increase in the force amplitude in the source at the frequency f-r=v-st/(2L), where v-st (ca. 5000 m/s) is the velocity of compressional wave in steel rod. This frequency interval is not wide; therefore, to have an even spectrum of the summary signal in the interval 60-120 Hz, the vertical grouping is needed. The latter must be performed at the depths L = 20-32 m with the small step delta L similar to 1-1.5 m. At different depths, other steps of delta L may be chosen to ensure the better suppressing of satellite-waves.
первоисточник: Геология и геофизика