Hugh Bradner

Investigation of microseism sources with ocean-bottom seismometers

Recordings to depths of 5 km have been made on the Pacific Ocean bottom with self-rising internally recording seismometers. Simultaneous recordings have been made at land stations. The ocean-bottom noise spectrum is between one and five orders of magnitude higher power than the land spectrum in the region from 0.1 to 9.0 cps. Coherence between two simultaneous instruments separated one-quarter kilometer is above the 95 percent confidence level from 0.1 cps to 0.6 cps. Attempts to associate narrow-beam Love and Rayleigh peaks with large storm-generating areas or with heavy swell striking shore have not produced consistent results. Although some records show the bulk of the microseism peak energy in well-defined modes, the energy is carried in different modes at different times and locations. Some of our data fit a model of microseism generation in a 100-mile strip, by a statistical superposition of incident waves and waves reflected from shore; and the subsequent conversion of the energy to Rayleigh and Love modes propagating away from the generation zone. However, the shapes of the mid-ocean spectra strongly imply additional sources far from shorelines or recognized storms, unless microseisms attenuate far less in the ocean than on land.

Coherence measurements with time sampling ocean-bottom seismometers

Instruments for obtaining simultaneous records of ocean-bottom seismic motion are described. Preliminary ocean-bottom seismic data with two simultaneous three-component instruments indicates that instrument noise and water currents may cause small differences in the detailed spectra. The general features of the spectra, however, appear to be the same from proximate instruments.

Range Energy Relation for Protons in Nuclear Emulsions

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Internal Navigation without Gyros

The horizontal displacement of an object can be determined by multiply integrating the outputs of two ideal accelerometers mounted on a pendulum on the object. The result is independent of the time history of the displacement or tilts. It is also independent of the damping and natural period of the pendulum, provided that the integration extends from before the displacement occurs until after the pendulum comes to rest.

Biophysical limitations on deep diving: Some limiting performance expectations

Decompression is treated according to the conventional Haldane model, but with continuously varying gas mixture, and continuous ascent.

Microseism propagation via oceanic waveguide

SummaryExperiments have been made to determine whether a significant amount of microseism energy in the open ocean can be carried in organ-pipe π waveguide modes. A three-component seismometer in a spherical aluminum container was balanced to float freely at midwater depth; a similar instrument was dropped on the ocean bottom. Simultaneous records from the two instruments were analyzed for peaks in coherence of their power spectra. Results indicate a substantial energy in π modes in the ocean area of the observation, though the peak power appears in an unidentified mode with large horizontal motion of the water.Measurements at the same area, but widely separated in time, indicate that the frequencies of microseism peaks and the general shape of the microseism spectrum are characteristic of the geographicallocation, in agreement with the conclusion of Monakhov. The microseisms are characterized as motion in a wave guide that is excited by a non-white forcing function.

The\(\dot V_A /\dot Q\) resolution of inert gas dataresolution of inert gas data

The non-uniqueness of\(\dot V_A /\dot Q\) distributions satisfying inert gas retention data without error is studied. The ability of such data to resolve blood flows at particular\(\dot V_A /\dot Q\) values is discussed through the application of linear programming and Backus-Gilbert theory. It is shown that the resolution deteriorates away from the extremes of low and high\(\dot V_A /\dot Q\).AbstractThe non-uniqueness of

Comparative seismic noise on the ocean bottom and on land

\dot V_A /\dot Q