Periodic variations of the gravitational force. A gravity survey in the Monk Hill area. Transmission of shot impulses in shallow water.

gravitational force, gravimeter, Mt. Wilson, Raymond Basin, San Rafael Hills, Monk Hill, ground waves, water waves

Geldart, Lloyd Philip ; Dix, Charles Hewitt

University:California Institute of Technology

Department:Geological and Planetary Sciences

关键词: gravitational force, gravimeter, Mt. Wilson, Raymond Basin, San Rafael Hills, Monk Hill, ground waves, water waves;   

Others  :  https://thesis.library.caltech.edu/5989/1/Geldart_lp_1949.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

Part I:Using a La Coste and Romberg gravimeter, readings were taken every half hour for 72 hours immediately preceding full moon in the sub-basement of Mudd Building, California Institute of Technology, and for 56 hours immediately following in the interferometer building on Mount Wilson.Observed values were compared with values calculated on the hypothesis of a rigid earth, the results showing more yielding at Mount Wilson (22%) than at Mudd Building (16%).Effects due to ocean tides and barometric changes were estimated.After the removal of drift and earth tide effects, the residuals showed periods of 24, 12, 6, and 2 hours, the 24 hour period being very strong at Mount Wilson.

Part II:Using a La Coste and Rombert gravimeter, gravity values were obtained at 65 stations in the vicinity of Monk Hill, Pasadena.A density value for elevation corrections was obtained using a least squares method and data obtained with a network of 35 stations in Washington Park.A topographical correction was also made for the San Gabriel Mountains to the north of the area.

The corrected gravity data were used to calculate elevations of the basement along Howard Street, and the resulting basement profile compared with one obtained by a seismograph survey.

Part III:The properties of various types of waves set up by underwater explosions is discussed from the viewpoint of their application in locating shot points in seismic work carried on over water.The construction of the audio amplifiers and filters used to record these waves is described, together with the results of a preliminary check of their performance.