Page 153 - GIS for Science, Volume 3 Preview

Acoustic propagation modeling can be used to estimate or predict natural and anthropogenic sounds underwater. The natural soundscape consists of everyday noises, such as wind, waves, and marine mammal communication, and more unique sounds, such as cracking and ridging ice or earthquakes (pictured in map A is the March 1964 earthquake in the Gulf of Alaska, the strongest ever recorded in North America.).
Anthropogenic sounds also fall into two categories of common sounds and unusual events. The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) has a worldwide monitoring network in place to make sure that one of the most devastating unusual events (testing of nuclear weapons) doesn’t happen, and if it does happen, the international community is aware of it immediately. Pictured in map B is the hydroacoustic portion of the CTBTO international monitoring system, with the red dots representing the acoustic moorings and the colored raster images illustrating the coverage of the monitoring network with the colors representing how loud a source would be in the network.
B
A
Map A simulates the sound of the magnitude 9.2 earthquake in the Gulf of Alaska on March 27, 1964. The color red symbolizes received sound levels of more than 130 decibels. Earthquakes can sometimes be detected on hydrophones around the world, illustrating the importance of accounting for 3D propagation effects, which can be sub- stantial over great distances. Map B represents
the coverage of the CTBTO global monitoring array. Acoustic propagation is largely reciprocal, which means the same simulation software used to model how loud a source such as an earthquake would be all over the ocean also can show how loud a source in any position in the world would be on a network of hydrophones, such as shown here. At any location shown in light blue, yellow, or red, hydrophones would detect an explosion.
The Science of Ocean Acoustics 141