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Shallow Reflection Seismics Using Firecrackers As The Source
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 5th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems, Apr 1992, cp-210-00026
Abstract
Due to the high resolution requirement of shallow reflection seismics, a<br>firecracker source was invented to generate high frequency signals used in<br>studying shall ow structures. Except for a slightly lower energy level, the<br>firecracker source has proved to be efficient, portable, cheap and safe. Its<br>performance was satisfactory. In this paper, a field test in a good<br>reflection area was conducted to exhibit high frequency signals among the<br>massive noises of groundroll when delineating the underground layers. By<br>setting the geophones at the near as well as the far offset distances, we<br>obtain different but compatible seismic profiles which could provide us with<br>different structural details. Careful and properly adjusted field procedure<br>has always been a key factor for successful shallow seismic reflection studies.<br>The other purpose of this paper is to use the firecracker source for<br>investigation of near-surface faults whose locations are only grossly known.<br>Three seismic lines, one used in detecting the Hsincheng fault and the other<br>two the Shihtan fault, were shot. They all resul,t in good reflection images<br>illustrating the structural variation across the fault. This kind of<br>near-surface fault mapping provides very detailed information about the<br>fault and the structure, which can be used to understand the faulting<br>processes during the earthquake. It is believed that the developed technique<br>could work equally well for other engineering applications. On account of<br>the outstanding achievements of firecracker source, we may expect a wider<br>acceptance of this powerful method for shallow structure studies in the future.