Seismic surveys within the Oceanic Shoals CMR, 1976-2010

Seismic surveys have been used extensively in Australia by Geoscience Australia to map undersea geology and by various companies exploring for oil and gas deposits, particularly on the NW shelf (for example, at Scott Reef in 2007). In such surveys, ships tow multiple airgun arrays that emit thousands of high-decibel explosive impulses. These highly energy sound waves can penetrate up to 40 km into the seabed before bouncing back to be recorded as echoes by an array of hydrophones. The speed and intensity of these echoes enable 3D mapping of the structures within the seabed (see example).

The airgun blasts are as loud underwater as the noise of a jet taking off at a distance of 100 m on land. In the immediate vicinity of the blasts, this can harm a range of marine wildlife, whether by direct physical impacts (hearing loss, injury) or disruption of behavior (eg, whale strandings). As the blasts are primarily low frequency and travel great distances (1,300 to 3,000 km) through the oceans, they may also make it harder for marine megafauna like whales to communicate with each other by making the ocean too noisy (for example, see this recent paper and this recent paper). In 2008, this led Environment Australia to issue industry guidelines for the interaction between offshore seismic exploration and whales as part of the 1999 Environment Protection and Biodiversity Conservation Act.

Use the interactive map below to see where seismic surveys have been conducted near or within NW Australia's Oceanic Shoals CMR. Click on the icon with four arrows at the top left of the map to see a full screen version. Then, you can choose to view 5 year compilations of survey data from 1976 to 2010.

How to use the map

	Click on this icon at the top left of the map to see a full screen version.
	Click on this icon also at the top left of the map to zoom in closer to (+) or further from (-) the map.

Click on the 5 year block of seismic survey data that you want to view in the list of overlay layers to the far left of the map. If a 5 year block of data is already checked in the list, you'll need to click on it to turn it off.