Due to the high resolution requirement of shallow reflection seismics, a fire-cracker cource was invented to generate high frequency signals used in studying shallow structures. Preliminary tests have been done to evaluate its feasibility (Tsai et al., 1991, paper I). Except for a slightly lower energy level, the firecracker source has proved to be efficient, portable, cheap and safe. Its performance was satisfactory. In this paper, a further field teat in a good reflection area was conducted to exhibit high frequency signals among the massive noises of groundroll when delineating the underground layers. By setting the geophones at the near as well as the far offset distances, we obtain different but compatible seismic profiles which could provide us with different structural details. Careful and properly adjusted field procedure has always been a key factor for successful shallow seismic reflection studies.
The other purpose of this paper is to use the firecracker source for investiga­tion of near-surface faults whose locations are only grossly known. Three seismic lines, one used in detecting the Hsincheng fault and the other two the Shihtan fault, were shot. They all result in good reflection images illustrating the structural varia­tion across the fault. This kind of near-surface fault mapping provides very detailed information about the fault and the structure, which can be used to understand the faulting processes during the earthquake. It is believed that the developed tech­nique could work equally well for other engineering applications. On account of the outstanding achievements of firecracker source, we may expect a wider acceptance of this powerful method for shallow structure studies in the future.