The seismic reflection team is four people strong. Some of us are well-seasoned Greenland voyagers and some of us are first timers, but we are all eager and exited to explore the Petermann area, an area where to our knowledge no seismic data exits, yet. We are going to change that!
What are reflection seismics?
The seismic reflection method makes use of the properties of the velocity of sound. When we create a sound at or near the surface of the Earth, some energy will be reflected back (bounced back). These reflections can be characterized as echoes. From these echoes we can determine the velocities of the rocks and each rock or sediment has a different sound velocity. We can also find out the depths where these echoes came from. This method is actually very comparable to the sonogram technique doctors use to visualize an unborn baby in a woman´s womb. In a way, we are “talking” to the Earth.
Consequently, reflection seismics is a non-destructive technique that allows Earth scientists to quickly get a good overview of the Earth´s internal crustal structure, hidden below meters of water and the seafloor.
To create these images we will be towing an acoustic source, which will send the sound waves, and a whole array of hydrophones, which will register the echoes, behind the ship. Depending on the frequency of the sound wave we can image the deeper parts of the Earth´s crust, but in a low resolution or only the upper parts of the Earth´s crust, but in a much higher resolution. That is why we will be using two types of acoustic sources: a GI Gun, which sends out low frequency sound waves and a Sparker, a source that sends out higher frequency sound waves.
During the Petermann expedition we are one of the first teams that will get some action. We are the explorers who will give all marine teams a first view what is concealed by the ocean water. The reflection seismic data will allows us to visualize the sediment infill of the different ocean and fjord basins. This data will be crucial when selecting the best sediment core locations. It will also help in tying the whole evolutionary story of this area together, since all the seismic reflection lines will be connected, so we can have an idea how the different basins and different geological processes interacted with each other through time.