For those who do not know Seismology is the science that studies earthquakes and related phenomena and is used in oil exploration. In the old days, on land, holes were drilled at intervals and pots (geophones) were placed at specific intervals and then you would shoot the holes. That meant blasting the holes with small explosives in a precise sequence and recording the seismic wave that is reflected through and by the substrata. These waves were recorded on LONG rolls of paper (logs) and studied in detail by geologists to predict the presence of formations likely to produce oil. Most likely the source of the seismic wave has been upgraded and there are certainly no longer long rolls of paper. Instead there are computers and programs to aid the geologist is his search for oil.
Seismic data acquisition of sedimentary layers in a seabed beneath a large body of water such as an ocean has traditionally been used to acquire images of underlying oil fields to facilitate the recovery of oil reserves. Such data acquisition enables offshore drilling sites to be established by indicating possible locations in which to extract oil. Seismic data acquisition involves generating seismic waves from a source and receiving or "listening" to a reflected or returning wave that carries information about the medium through which it has passed.
Conventional seismic sound sources for underwater seismic data acquisition have typically operated by mechanically generating sound from the rapid release of compressed air using an air gun, or from the mechanical impact of metal on metal for some other applications.
Air guns operate near the ocean surface, often approximately 7-10 m below sea level, and operate by firing a pulse that, though partially directed downward, is essentially omni-directional. A great deal of the air gun's energy is reflected off the seabed and remains trapped in the water column. This causes two immediate problems. First, to image properly deep reservoir targets, a large energy pulse needs to be generated and since the pulse length is short for acceptable seismic resolution (i.e., the ability to image thin layers), the sound levels need to be high. This large energy pulse is central to environmental concerns for marine life.
The second problem is the high sound level trapped in the water column. As noted above, most of the energy bounces off the seabed and is reflected back toward the surface. However, the sea surface is also reflective and sends the energy back down. This echo bounces off the seabed and the process repeats itself. These water bottom "multiples" are typically very large in amplitude and tend to mask the desired reflection data from the deep sedimentary layers. Although techniques have been developed for removing these water bottom multiples, this inherently requires additional processing and risks disrupting the actual data that is desired from the original reflection.
In addition to the environmental concerns and the high sound level trapped in the water column, the use of an air gun is relatively primitive in the type and amount of data that can be carried in a reflected signal. Moreover, the air guns typically need to be dragged along behind a vessel or attached in some way near the surface of the water body, which requires additional equipment, time, and effort and could get in the way of fishing nets or any other equipment that operate in the few meters below the surface where the air gun operates.
The type of seismic wave generation that would be used in Belize waters has yet to be established but probably the cheapest available method would be used. Although offshore drilling has proven safe in most cases the impacts of a seismic survey in the shallow waters of Belize on the fish population, breeding habits and other poorly understood factors must be considered and studied before seismic exploration is allowed. Studies have shown relationships between species behavioral changes and seismic activities that are not fully understood. Shallow water in drilling lingo is less than 2,000í. Most of the major species including the Nassau Grouper have spawning aggregations in certain areas outside the reef in little understood processes. It would seem that seismic wave generation unless using the most advanced equipment would likely affect these aggregations and if carried out inside the reef probably have a higher impact. Fish seem to be particularly sensitive to noise and sound travels several times faster underwater than in the air. As we all know throwing dynamite into the water kills surrounding fish due the sonic wave created.