Abstract
Horizontal strains in the earth crust can be calculated from the geodetic data and the knowledge of the strains plays an important role in the earthquake prediction. There, however, are only a few reports which discussed about the accuracy of the estimation of the magnitude of strains in the crust. In this paper, a general formula is deduced to calculate the accuracy of strains from the small changes in the position of geodetic control points. The formula is applied to calculate the strains in the Surugabay area, where the occurence of a great earthquake is predicted. According to our theory, the strain rate of this area is about (3.1±1.2)×10-7 per year. Using this value, cumlative probability of the great earthquake occurence and its 68% confidence limits are also calculated.
