The International Association of Geophysical Contractors published the following article on the IAGC website:
“Published on August 16, 2017
Andrew Long
Chief Scientist, Geoscience & Engineering at PGS | Geophysicist | Structural Geology
Offshore exploration for oil and gas is increasingly confronted by opposition to seismic surveys. For some, the opposition is motivated by an ambition to replace all fossil fuel dependency with renewable energy sources such as solar, wind, geothermal and so on. For others, the opposition is motivated by concerns about the impacts of seismic noise on marine fauna and their habitats. In the latter case there is a wealth of knowledge available on the physics of underwater acoustic noise, but sensational claims are often made about the potential physiological and behavioral effects of acoustic noise on marine animals at various ranges, magnitude and duration. In reality, there has been no documented scientific evidence of noise from air guns used in geological and geophysical (G&G) seismic activities adversely affecting marine animal populations or coastal communities, and the only ‘scientific’ publications that describe physiological damage involved the deliberate firing of air guns in the immediate proximity of marine animals for sustained periods.
The activity of seismic surveys in areas designated as environmentally sensitive is regulated by a series of established ‘received sound metrics’ which include sound pressure level (SPL) and sound exposure level (SEL); together applicable to both impulsive and transient acoustic noise types. Specific SPL and SEL thresholds are used to dictate how surveys may operate at various distances from either observed marine mammals, marine parks, commercial fisheries, and so on. An example of such underwater acoustic thresholds can be found here.
Unfortunately, emotive and unfounded tactics by opponents of seismic surveys, and indeed, oil and gas exploration itself, are not conducive to productive engagement between the exploration companies and the many stakeholders in each region. To put emotive tactics into perspective, consider the latest campaign from a well-known activist group in one region:
How do you stop an oil company – or several?
This is not a normal question for most people. But if you’re a <ACTIVIST> kind of person, you get it. You get that Big Oil poses a threat to our entire planet. You get that the fossil fuel era must come to an end, and renewables must be allowed to rise.
The mother whale is distressed. She can’t find her calf. The onslaught of deafening noise from seismic testing has overloaded her senses. She’s lost, panicked and alone – and so is her baby. Both may begin bleeding from the middle ear and brain. They could beach themselves. Or merely starve to death, slowly.
It’s horrendous, brutal and largely invisible to humanity. And Big Oil is getting ready to do it all over again. Right now <COMPANY A> is planning its exploratory drilling, just as <COMPANY B> and <COMPANY C> want to begin their own seismic testing inside the majestic waters of the <LOCATION>. They must be stopped – all of them. And <ACTIVIST> can’t do it without you.
Imagine cannon blasts going off next to your head every few minutes, 24 hours a day, for days and even months on end. That’s seismic testing: where oil companies shoot air guns down into the seabed at volume levels comparable to a space shuttle taking off.
Now imagine you’re dependent on your hearing to not only hear but ‘see’ – navigate, communicate, find food and keep your family close. Scientists have recently discovered that baby whales and their mothers even ‘whisper’ to each other to avoid predators. Turning their home into an oil field means seismic testing, increased shipping traffic and noise pollution….and all this disorienting noise makes calves easy prey. It is absolutely devastating – and for what? More toxic fossil fuels choking our atmosphere and threatening life on Earth.
These mothers and babies need each other. Together we will protect them, the beautiful <LOCATION> and our planet, before it’s too late.
Such hysterical claims are grossly exaggerated and untrue but of course they attract attention, and that’s the point of the exercise. So let’s have a brief look at how seismic surveys use ‘air guns’–actually canisters releasing compressed air, to produce the acoustic energy that works like a very low frequency version of ultrasound medical diagnosis to similarly see below the surface of the earth. To put things into context, the hearing range of a human child is about 20 to 20,000 Hz, being most sensitive over the range of about 1,000 to 5,000 Hz. Large marine mammals have comparable hearing ranges and sensitivity, albeit extending to even higher frequencies. Seismic surveys are most interested in the 2-100 Hz range as these frequencies reveal the most information about the geology below the surface.
Are Air Guns Like ‘Cannon Blasts’?
The short movie below shows an observer with a video camera seated in workboat as they approach a standard air gun array being fired at an interval of several seconds. The main vessel towing many seismic streamers; each containing thousands of passive listening devices known as hydrophones, can be seen in the distance. The same vessel also tows air gun arrays, connected to the vessel by very long air hoses and various electronics. When the workboat is alongside the air array the camera is placed below the water, only a few meters from the closest air gun. The effect of the air guns being fired is, perhaps disappointingly, nothing like ‘cannons’ being fired or space shuttles being launched. A dull thud is perceptible, a small cloud of bubbles forms around each air gun, they drift away behind the array, and then the process repeats some 8-10 seconds later.
But let’s not let the truth get in the way of a good story…
So far it has been very easy to flood the social media space with extremist claims about unethical impacts of oil and gas exploration upon marine fauna. I suggest it’s time the offshore exploration industry started transparently showing the public how surveys are really conducted and what the impacts are during those surveys. As is the case here, a short video says a thousand words. No one questions anyone’s desire to protect the environment we live in, or the passion that many people have for their ambitions of the future. The world is slowly moving towards renewable energy alternatives at a pace that is sustainable and affordable, but hydrocarbons will be by far the essential energy source of energy and many consumable products for the forseeable future. We all in fact share the ambitions of a clean and healthy world, and we can all get there without hysteria, fake science, or a refusal to talk openly about simple and approachable topics such as the acoustic profiling of marine geology using seismic surveys.
