Crustal Strain and Probability of Earthquake Occurrence

概要

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Statistics of ultimate strain of the earth's crust is made on the basis of levelling and triangula-tion data over earthquake areas. The mean value of ultimate strain so is obtained as 5.3 × 10-5 with a standard deviation Q amounting to 3.3× 10-5 on the assumption that the deviation from the mean value is governed by a Gaussian distribution. Assuming that crustal strain increases linearly with time t from an appro×imately zero value immediately after an earthquake, which occurred at t=0, the probability of having a crustal break or an earthquake occurrence during a time in-terval from 0 to t can be calculated from Eo and σ along with the data for strain accumulation over the area concerned as brought out with repetitions of geodetic survey. Applying the above theory to an area south-west of Tokyo, where an earthquake of magni-tude 7.9 took place in 1923, the probabilities for repetition of a similar earthquake there are esti-mated as 0.2, 0.5 and 0.8 for periods 1925-1980, -2030, and -2080.
日本測地学会の論文