Simulation Method of Airgun Pulse Impacts on Marine Mammal Utilizing ARGO Date and Ocean Bathymetry Date by Google Earth

Abstract

Abstract:Japan is a small island country surrounded by a vast EEZ which is thought to contain rich offshore resources, such as oil and natural gas. Recently, seismic surveys have been carried out to locate such resources. Because of their high resolution, seismic surveys are predicted to increase in the future.However, these surveys utilize air guns, which generate intense and low-frequency impulse noises known to disturb and harm marine mammals. The impact of seismic survey noise on marine mammals began to attract attention in the early 1970s, and acoustic impact thresholds and mitigation measures are still discussed all over the world. Here we propose an assessment method utilizing ARGO data and ocean-bottom topography data from Google Earth. We studied influences by seasonal climate changes and ocean-bottom topography with respect to the results of impact assessment, and found that these gave meaningful differences to our assessment results. This finding suggests that our proposed method is adequate for assessing the impact of seismic survey noise on marine mammals. We also assessed received levels of noises generated by air guns in a cetacean habitat near the Ogasawara Islands, utilizing the proposed method and the newest acoustic impact thresholds as updated in March 2016 by NOAA.