What energy sources can I use for my seismic investigation?
Depending on your application and target depth, the energy source for a seismic investigation will differ. The most common seismic sources for ground investigations on land are listed below, together with suitable investigation depth.
Sledgehammer 0 – 30 meters A sledgehammer is a cheap and simple solution but with limited depth. A sledgehammer is normally used with some kind of strike plate to improve the transfer of energy from the hammer to the ground. These plates can be either metal or plastic, with the latter typically giving a ‘cleaner’ source pulse, which has a slightly lower frequency component than the metal equivalent.
‘Buffalo gun’ 0 – 50 meters A type of shotgun, used with the barrel pushed or screwed into the ground. It is used with shotgun shells and gives a good, low effort energy source.
Vibration units 50 – 100 meters There are a number of different vibration units available, but they share a common design: a variable speed motor driving a weighted plate which sits directly on the ground, and which can oscillate through a range of frequencies. The systems are designed to achieve both good penetration as well as excellent resolution and are very useful for surface wave and reflection seismic methods.
Weight drops 40 – 1000 meters Weight drops can be used for shallow to deep investigation, ranging from smaller handheld units, which rely only on gravity to accelerate the weight, up to larger vehicle mounted equipment which mechanically accelerate the weight towards the ground beneath them. A weight drops provide excellent repeatability which makes the process of stacking shots (to improve the signal quality) far more effective.
Explosives 0 – ? meters Mechanical solutions that are suitable for large depths can be quite expensive and, by necessity, very large. The cheapest way to generate a large seismic pulse would be with explosives but clearly there are complications with this, and not only from a safety point of view, but there will also be legislation upon purchase, storage and use. Explosives can be used on land or in water and often the explosion and the only limit on depth is the size of charge you have available / are licensed to use.
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