The Analysis of Monthly Mean Sea-Level

Abstract

The modified difference method is derived for the analysis of the monthly mean sea level. This method consists of taking the difference of monthly mean sea-levels between the standard and reference stations in a same region and cancelling the annual variation. The irregularities left after the correction of this method are rather reduced and are estimated as about ± 15 mm. In the Niigata Earthquake; 1) It seems to be difficult to detect the extraordinary changes before the Earthquake, though the slight change of linear variation might exist around 1959. 2) The displacement of the crust at the Earthquake are motionless in Iwasaki, a score of centimeters down in Nezugaseki and a few centimeters down in Wajima, being based on Kashiwazaki. 3) The difference of linear variations between Nezugaseki and Kashiwazaki might change before and after the Earthquake. Such phenomenon is found at Kushimoto before and after the Nankaido Earthquake. In the Tokachi-Oki Earthquake, 1968; 1) It seems likely that the crust around Hachinohe and Miyako subsided by several centimeters comparing with that of Onahama. 2) It is possible that the abnormal change appeared in 1966 might be related with the oceanographic conditions. © 1969, The Geodetic Society of Japan. All rights reserved.