A study on the design of small-scale columnar phase change seismic source and wavefield characteristics

Abstract Gas explosion sources offer advantages such as environmental friendliness and strong explosive energy, making them an important component of current blasting and seismic exploration sources. We proposed a small columnar phase change seismic source model consisting of internal explosive system and external autogenous heat system. First, we analysed the displacement radiation patterns generated by this seismic source in different directions based on a far-field point source. Combining three-dimensional wavefield simulations, we revealed the propagation characteristics of wavefields excited by sources in different directions at shallow depths. Then, we developed a columnar phase change seismic source with a diameter of 5 cm and a height of 10 cm using materials such as ammonium bicarbonate, aluminium alloy, and aluminium-based heating packs. Finally, a comparative analysis was conducted on the propagation characteristics of field observation signals generated by the developed columnar phase change seismic source and a 3 kg hammer-impact seismic source. The results indicated that, compared to the hammer-impact seismic source, the seismic signals produced by the explosion of the columnar phase change seismic source were stronger, capable of propagating to distances exceeding 70 m, with waveform consistency exceeding 94% across five excitations. Furthermore, the signal bandwidth was wider, with a dominant frequency range of 30–65 Hz. The propagation characteristics of seismic signals were verified by simulation results. The small columnar phase change seismic source can be used as an alternative seismic source in seismic exploration applications such as urban underground space detection and shallow surface seismic exploration, with broad application prospects.