Temporal change of the vertical crustal movement on the western coast of Suruga Bay, central Japan

We investigated the spatial pattern of vertical crustal movement and its temporal change in the eastern Tokai region, central Japan, on the basis of leveling measurements by the Geographical Survey Institute of Japan. In order to analyze the data along the leveling route between Kakegawa (BM140-1) and Hamaoka (BM25951), we used the program BAYSEA to see how the trend of subsidence at BM25951 relative to BM140-1 has changed since 1982. We found that the subsidence accelerated in the period of 1987–1989 and has been decelerating since then. The average spatial pattern of vertical displacement in the eastern Tokai region for the last 18 years is characterized by conspicuous subsidence along the western coast of Suruga Bay with a gradual decrease of the subsidence rate in the inland direction. The spatial pattern, however, was noticeably different during the period when the subsidence at Hamaoka relative to Kakegawa was accelerated: the subsidence rate at that time was larger in the northern part of the western coast of Suruga Bay compared to that in the southern part. On the other hand, it seems that subsidence on the western coast of Suruga Bay has been decelerating in late 1990s.