Crustal Deformation in and extended Area after the 1946 Nankai Earthquake Deduced from Tide Gauge Records

Abstract

We investigated crustal deformation after the 1946 Nankai earthquake using tide gauge records. Although resolution of tide gauge records is not so high for seeing the temporal change in detail, vertical crustal movements whose relaxation times are between several months to years can be detected by them. It was reported that there had been a postseismic crustal deformation with a time constant of 4-5 months in southern Kui Peninsula (Kobayashi et al., 2002). In this paper we show that crustal deformations with a longer relaxation time of a few years were observed in northern Shikoku, examining tide gauge records at such stations as Takamatsu, Sumoto and Kobe. These observations suggest that there was a time lag in the development of postseismic slip between shallow and deeper parts on the plate interface after the Nankai earthquake.