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Documentation of a FORTRAN program, 'isocomp', for computing isostatic residual gravity

1981; United States Department of the Interior; Linguagem: Inglês

10.3133/ofr81574

2332-4899

R. C. Jachens, Carter W. Roberts,

Geomagnetism and Paleomagnetism Studies

FORTRAN program 'isocomp 1 computes isostatic residual gravity from input data consisting of gravity station coordinates, complete Bouguer gravity and topography digitized on a geographic grid.It is based on the assumption of complete local isostatic compensation according to the Airy-Heiskanen system.The program requires numerical values for the assumed sea level crustal thickness, density of the topography, and density contrast across the Moho.The program is designed for operation on the U.S. Geological Survey's Honeywell computer using the Multics operating system.As many as 2700 stations can be processed during a single run and the cpu time is approximately 3.2 seconds per station. PrefaceThe program is designed for operation on the U.S. Geological Survey's Honeywell computer using the Multics operating system.The program has been extensively tested for stations located in North America where latitudes and longitudes are positive, so care should be exercised in the use of negative latitudes or longitudes.The maximum number of stations that can be input is 2700.The program is written in Multics FORTRAN and is basically compatible with ANSI 66 FORTRAN.In transportation to another system, the calls to the Multics external subroutines io and close-file will need to be replaced by appropriate opening and closing file routines.In addition, most systems will require the program to be in upper-case.The supplementary FORTRAN program, isoworld, (also documented in this report) for computing the combined isostatic and topographic corrections requires the Surface Gridding Library routines bgngrd, setgrd, clchgt, and endgrd for constructing a grid from the table and reading the interpolated values for the correction at each station.The Multics external subroutines asr, dsr, and close-file are used.The commands asr and dsr are used to locate the surface display routines on Multics.