Aarhus University Seal / Aarhus Universitets segl

No. 161: Onshore Seismic Surveys in Greenland

Kyhn, L.A., Wegeberg, S., Boertmann, D., Aastrup, P., Nymand, J. & Mosbech, A. 2020. Onshore Seismic Surveys in Greenland. Background information for preparation of Guidelines to Environmental Impact Assessment. Aarhus University, DCE – Danish Centre for Environment and Energy, 56 pp. Technical Report No. 161 http://dce2.au.dk/pub/TR161.pdf

Summary

This report contributes to the background information required to develop guidelines for how to conduct terrestrial seismic surveys in an environmentally responsible fashion. The report contains seven chapters that are briefly summarized in the following.

 

Ch. 1. Seismic surveys are conducted to examine hydrocarbon deposits deep below the surface of the Earth. There are a number of techniques to perform them, but generally a signal is transmitted into the ground and the resulting echoes and reflections are picked up by hydrophones placed on the surface. These reflections and echoes are hereafter analyzed. Seismic surveys may be carried out as 2D, 3D or 4D, which reflects the grid size and time dimension.

 

The techniques used to day are either a seismic vibrator, i.e. vibroseis, or explosives. Vibroseis are conducted by heavy trucks that vibrates a plate to the ground to project a low frequency signal downwards. The signal is then reflected and refracted before it returns to the surface and is recorded with geophones placed on the ground. Geophones can be wireless or inter-connected. When explosives are used, small amounts are ignited app. 4-10 m below the surface to create the low frequency signal. The reflected/refracted signal is recorded by geophones.

 

Ch. 2. Effects on the environment depends on the chosen method and on the time of year the survey is conducted. It is however often conducted with very large and heavy trucks, which can leave large imprints in the landscape by damaging the vegetation and the organic crust, whereby permafrost and hydrology can be altered leading to erosion and terrain damages such as thermokarsts and subsidences. Such disturbances can persist in the Arctic for over 70 years or disappear slowly with time. Seismic surveys can also cause strong disturbance reactions in wildlife and birds.

 

Ch. 3 and 4. Terrestrial seismic surveys were conducted in Jameson Land, East Greenland, in the 1980ies. The surveys were conducted both summer and winter. A number of environmental investigations as well as monitoring were conducted prior to, during and following the seismic surveys. The results of these are part of the foundation for the recommendations for mitigation proposed in this document. A number of possibilities exist whereby the disturbances may be decreased, which pertain to type of vehicle and season; amount of snow and hardness of the ground (frozen).

 

Ch. 5. The purpose of developing guidelines is to minimize the negative effects on the environment. DCE/GN recommends in this report that an Environmental Impact Assessment (EIA), alternatively an Environmental Mitigation Assessment (EMA) is carried out during the application process for conducting terrestrial seismic surveys. It is also recommended to conduct baseline studies in order to evaluate the adequate measures necessary to ensure as small as possible negative effect on the environment.

 

Ch. 6 and 7. A number of publications exists on the subject, which is reviewed a long with an overview of the background reports of the Greenland studies.