Improved methods for measuring present crustal movements

Improvements in geodetic measurement techniques are likely to play an important role in a number of types of geodynamics studies during the next decade. Increased accuracy for horizontal distance and gravity measurements at many sites is expected using mutliple-wavelength measurements and falling-retroreflector gravimeters. Improved tiltmeters and strainmeters are being developed, with attention being given to decreasing perturbations due to very local ground noise. Geodetic receivers using signals from the Global Positioning System satellites probably will make possible rapid relative position measurements with 1 to 3 cm accuracy in and around seismic zones. An international program of worldwide position measurements with about 3 cm accuracy is planned, using both laser range measurements to the LAGEOS satellite and long baseline radio interferometry.