Hydroacoustic Propagation Through the Antarctic Convergence Zone: Study of Errors in Yield and Location Estimates for Explosive Charges

• Main Authors: de Groot-Hedlin, C., Blackman, Donna K., Jenkins, C. S.
• Other Authors: NAVAL SURFACE WARFARE CENTER INDIAN HEAD DIV MD
• Format: Text
• Language: English
• Published: 2007
• Subjects: Atomic and Molecular Physics and Spectroscopy; Physical and Dynamic Oceanography; *CALIBRATION; *DEPTH CHARGES; *TRAVEL TIME; *TRANSMISSION LOSS; *SPECTRAL ENERGY DISTRIBUTION; *ERRORS; UNDERWATER ACOUSTICS; NEW ZEALAND; ANTARCTIC REGIONS; AZIMUTH; POSITION(LOCATION); SIGNAL TO NOISE RATIO; OCEAN SURFACE; SYMPOSIA; UNCERTAINTY; SURFACE ROUGHNESS; *PROPAGATION MODELS; *NUCLEAR MONITORING; *ANTARCTIC CONVERGENCE ZONE; INTERNATIONAL MONITORING SYSTEM; Antarctic; Fernandez; Indian; New Zealand; The Antarctic; Antarc*; Antarctica
• Online Access: http://www.dtic.mil/docs/citations/ADA519212; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA519212

A series of small calibration shots was conducted in late December 2006, along a transect from New Zealand to Antarctica in order to document the differences in spectral characteristics, transmission loss, travel-time, and azimuth both observed and predicted using propagation models typical for nuclear monitoring. The high gradients in ocean temperature and salinity that characterize the Antarctic Convergence Zone (ACZ) are expected to alter the propagation path, and the commonly rough sea surface is likely to scatter significant energy from sources south of - 53 degrees S, where the sound channel breaches the surface. Seasonal variability in the ACZ makes it difficult to model such effects accurately at all times, so our experiment was designed to determine the scale of error introduced by such uncertainty in structure. Depth charges, set to trigger at 300, 460, and 600 m, were deployed at 6 stations between 54 degrees S and 63 degrees S. The International Monitoring System (IMS) hydroacoustic station off Cape Leeuwin, Australia, recorded shots from all but one site. Macquarie Ridge probably blocked that source area. Several shots were also recorded at the Diego Garcia and Juan Fernandez IMS stations. This new data set will be characterized in terms of source-receiver transmission loss and spectral characteristics, used to infer source yield, as well as source location errors. Preliminary analysis of arrivals at IMS hydroacoustic stations in the Indian Ocean indicates that the time duration of each arrival depends on source location, and not on source depth or size. Conversely, the spectral content of the signals depends on source depth and charge size, but not on the source location. Published in the Proceedings of the Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies (29th), held in Denver, Co on 25-27 Sep 2007, p697-702, 2007. Sponsored in part by the National Nuclear Security Administration (NNSA) and the Air Force Research Laboratory (AFRL). The original document contains color images.