Adjustment of relative gravity measurements using weighted and datum-free constraints

Chein-way Hwang*, Cheng G. Wang, Li H. Lee

*Corresponding author for this work

Research output: Contribution to journalArticle

48 Scopus citations

Abstract

A program in FORTRAN 90 is developed which can adjust relative gravity measurements and solve for gravimeter parameters using the weighted constraint and datum-free constraint models. The weighted constraint model is chosen when there exist reliable a priori gravity values for use as supplementary data, or when it is required that a gravity network be attached to an existing gravity network of a higher order. The datum-free model uniquely determines relative gravity values among all stations without the need of a fixed gravity value, thus it is suitable for detecting relative gravity change. The optional solve-for gravimeter parameters include drift coefficients, and coefficients of the long wavelength and periodic components of calibration function. The program can also detect outliers in observations using the ζ-test method. A set of relative gravity data in Taiwan was used to test this program using five different choices of command-line arguments. The results show that there are no outliers in these data and that the estimated reading accuracy of the LaCoste and Romberg G meter (serial number 838) is about 0.02 mgal and the gravimeter drift rate is 0.9 mgal/month. The coefficients of the long wavelength and periodic components of calibration function are statistically equal to zero. The result from the datum-free solution is used to detect gravity variation due to the 1999 Chi-Chi earthquake, concluding that only one station experiences a significant change.

Original languageEnglish
Pages (from-to)1005-1015
Number of pages11
JournalComputers and Geosciences
Volume28
Issue number9
DOIs
StatePublished - 1 Nov 2002

Keywords

  • Chi-Chi earthquake
  • Datum free
  • Gravimeter
  • Relative gravity
  • Taiwan
  • Weighted constraint

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