ALBERT

Description: The second half of CHAIN Cruise #11, 22 February until 22 March, 1960, is detailed as to type of measurements made with their specific locations. The cruise areas were in the St. Croix region, the Puerto' Rico Trench and the tracks from the Bahamas to Bermuda to Woods Hole. Camera lowerings, lowerings of the thermal probe and accompanying cores, dredging, sound velocimeter lowerings, and acoustic studies of the scattering layer were the special events undertaken while precision bathymetry and towing of the Continuous Temperature Recording Chain were on a watch standing basis.

Description: Undersea Warfare Branch, Office of Naval Research Under Contract Nonr- 1367(00) (NR- 261-10 2)

Description: The report presented is the final one under Air Force Cambridge Research Center Contract 19(604)·2157 with the Woods Role Oceanographic Institution. The report covers a program of pendulum and gravimeter measurements conducted over the period 1950·1959. The original objective of the program was to establish a series of reliable gravity control measurements through the use of pendulums over a sufficient range of gravity to permit the calibration of geodetic gravimeters with an accuracy of one part in 5000 over a range of 5000 mgals and thus assure a potential accuracy of 1 mgal or better with such gravimeters on any global series of measurements. With time this objective was modified to include the establishment of pendulum gravity measurements outside of North America as there appeared to be no unanimity of international opinion regarding a gravity standard. A second objective of the program was to expand the gravity coverage and standardize existing gravity surveys within the United States so that reliable gravity anomaly maps could be prepared. A third objective was to strengthen and expand the world network of airport gravity bases established earlier under the auspices of the Office of Naval Research so that data in all parts of the world could be integrated onto the same datum and gravity standard. The report is subdivided on the basis of these objectives into three principal parts plus an introductory chapter giving the history o~ the program, and a final chapter presenting recommendations as to further work deemed desirable. Dr. J. C. Rose, who has been in charge of the pendulum program since its inception, prepared the second portion of the report, which deals with the pendulum measurements, and the writer prepared the remainder.

Description: Work carried out under Contract AF19 (604)2157 with the Geophysics Research Directorate Air Force Cambridge Research Center Air Research and Development Command.

Description: The objective of this investigation was to measure bottom loss in normal incident reflection of pulses of twelve kcps sound and to study its geological significance. To this end a semi-automatic instrument system was developed which is capable of making continuous measurements of the peak pressure and the time integral of the square of the pressure of the sea floor echo, from a vessel underway. Observations were taken in both deep and shallow water areas in the Western North Atlantic. The early cruises were conducted in deep water to investigate the range and variability of bottom loss values. Geological control consisted mainly of a precise bathymetric record. The later cruises were conducted in shall ow water, in areas where the geology has been well studied previously by investigators using techniques of classical geology. In these latter cruises the acoustic measurements were correlated with a schedule of sediment dredging and underwater photography. Thirty-one thousand acoustic measurements were made. Median bottom loss values and standard deviations were computed and the results summarized in eleven hundred sets, each set corresponding to a location at sea. Seventy-seven sediment stations were occupied. A complete particle size analysis and a water content analysis were performed on these sediments to determine their size and mass characteristics . The size characteristics included the median grain size, the sorting coefficient, and the percentages of gravel, sand, silt, and clay. A sediment class name was determined from the gravel, sand, silt, and clay percentages according to the Shepard system of classification. The mass characteristics included porosity, bulk density, sound velocity, acoustic impedance, Rayleigh reflection coefficient, and theoretical bottom loss. The combined results show a good correlation between measurements of bottom loss and both mass and size characteristics of the sediment. The measured bottom loss increases as the porosity increases. The measured bottom loss also increases as the silt-clay percentage increases since the porosity of sediments generally increases as this fraction increases. It seems that the Rayleigh reflection coefficient can be used to predict acoustic bottom loss at normal incidence. Conversely, normally-incident bottom loss can be used under the assumption of a Rayleigh reflection process to determine the nature of the bottom sediment. The acoustical and geological results have been made available in tabulations, scatter diagrams, and as geographical plots. Except for the initial measurements, all operations, including the final displays, were accomplished through automatic digital processing machines.

Description: The Office of Naval Research under Contract Nonr-4029 ~ Nonr-13 67~ Nonr-1841 (74) ~ NR 083 -15 7~ and the Bureau of Ships under Contracts NObsr-72521 and NObsr-89464.

Description: Pendulum Program: During subject period Dr. Rose completed the rebuilding of the recording system for the pendulum so that visual records could be obtained with a standard oscillograph type camera. The first teat runs with this equipment showed that the accuracy of observataion was materially improved in that the period could be read with greater precision than was obtainable with the Berkeley counter direct read out system. A field run was made the last of October, which included observations at the following sites: Madison, Wisconsin Washington, D. C. Charleston, S. C. Key West, Florida Lamont Geological Observatory, N. Y. Otta, Canada Measurements were taken on a repeat basis on the return leg at each site and the reliability on the basis of a statistical analysis of the results was approximately 0.1 mgal.

Description: Contract AF19(604) 2157 with the Geophysics Research Directorate Air Force Cambridge Research Center Air Research and Development Command

Description: The theory of oblique-angle seismic reflectivity, as applied to oceanographic research, is presented. An experiment has been developed in which continuous oblique reflection profiles were made by towing an acoustic source behind a ship and listening with a hydrophone suspended beneath a free-floating radio buoy. Information received at the hydrophone was transmitted to the ship and recorded on magnetic tape. Energies of the bottom-reflected signals have been calculated for varying angles of incidence and the corresponding reflectivities produced. Results from the Tyrrhenian Sea and from north of Puerto Rico indicate the possibility that the sound velocity in the first-layer sediments is less than the sound velocity of the bottom water.

Description: The Bureau of Ships Under Contract NObsr-89464