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David R. Dall’Osto
Applied Physics Laboratory University of Washington 1013 NE 40th Street Seattle, Washington 98105 USA
The lost San Juan submarine was triangulated by the precision CTBT hydroacoustic network, which has great potential for ocean science.
Twenty years ago, the United Nations decided to collectively build what is, in essence, a stethoscope to continuously monitor the oceans in the world for the early detec- tion of the most serious danger to world peace and survival, nuclear explosions (see The impetus for creating this US$5 billion global network was to enforce compliance with the Comprehensive Nuclear Test Ban Treaty (CTBT). This network is designed to locate all types of nuclear tests (in the air, on land, underground, and underwater) to within an area less than 1,000 km2. The CTBT Organization (CTBTO) coordinates, maintains, and analyzes the data from these International Monitoring System (IMS) hydroacoustic stations along with the data from land- based infrasonic, seismic, and radionuclide detectors.
Six remote locations around the globe were chosen for detecting underwater detonations. Each location was instrumented with a set of sensitive hydrophones suspended deep within the ocean, at depths that would crush a submarine hull. The design of these moorings was optimized to measure sound propagating over great distances (see Figure 1 for the anatomy of an IMS hydroacoustic station). The record of ocean sound compiled as a consequence of the mission of the IMS network is a resource of vast potential for researchers in many fields, both for forward-looking and for historical scientific analysis.
Figure 1. “Anatomy” of an International Monitoring System (IMS) hydroacoustic station. Hydrophones are moored close to the axis of the SOFAR channel formed by the sound speed profile (left). Each station is composed of two triplets, one located on either side of the island housing the shore facility that telecommunicates the data (except station HA01 that has only 1 triplet; right). See text for details. Adapted from a figure courtesy of
Taking the Pulse of Our Ocean World
  20 | Acoustics Today | Winter 2019 | volume 15, issue 4 ©2019 Acoustical Society of America. All rights reserved.

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