山崎断層安富舂基線網における精密測地測量成果

Abstract

In order to investigate the behavior of the active Yamasaki fault, a pentagonal base linenet was set up across the fault at Yasutomi-Usuzuku (Hyogo prefecture) in July 1975.Since then, precise geodetic surveys have been carried out every year in November orDecember.The methods employed in the survey are horizontal and vertical angle measurementsusing a theodlite Wild T3, and precise base line measurement using several base line tapes.The angle measurements have been done at night for being freed from fluctuations of targetimages. The accuracy of the present observations is of the same degree as that for first ordertriangulation, consequently relative horizontal and vertical displacements of 1 mm would bedetected.In this report, the outline of the observational method and a part of the results from1975 to 1986 are described.