1. Field of the Invention
This invention relates to generating seismic waves, and is directed particularly to generating such waves for seismic geophysical surveying and like purposes using explosives. Specifically, the invention is directed to the explosive generation of seismic waves by forming a cavity below the earth's surface, filling it with an explosive gas mixture, and then detonating the mixture to produce the waves.
2. Description of the Prior Art
During about the first two or three decades of seismic geophysical surveying, virtually the only source of the desired seismic waves was the detonation of chemical explosives in a shot hole drilled to a depth below the weathering, despite the hazards of explosives-handling and the time and expense of drilling the shot holes. With the advent of data-processing and magnetic-recording techniques providing reproducible recordings, a great many alternate forms of seismic source became practical, such as vibrators, weight droppers, gas-gun and other impulse generators, impactors, and the like, all generally operating at the ground surface. Reproducible recording and data processing made these alternate sources practical by the possibility of summing the waves resulting from a number of relatively weak impulses, or time-compressing continuous-wave inputs which extend over long time periods, to provide the desired seismic-wave travel times. Most of these ground-surface wave generators are characterized by large masses, heavy mechanisms, complex mechanical systems, heavy transporting vehicles, and other attributes making them more or less costly to provide and use. In view of this, it is a primary object of my invention to provide a novel and improved explosive seismic source which does not require drilling deep shot holes, is self-contained, fast, safe, economical, and convenient to use, and causes a minimum of ground-surface damage.