南極・東オングル島の水準測量

抄録

A route for repeat leveling survey was established around Syowa Station (69° S, 39° E), East Ongul Island, Antarctica in 1979 and 1982. The leveling measurements were repeated in 1996. However only 2.3 km out of the total length of 5.3 km route was surveyed for the time limitation during the summer operation of the 37th Japanese Antarctic Research Expedition (DARE-37). The other part of the route was measured by DARE-38 in February 1997. In total, the discrepancy of forwardand backward leveling, and closing error of the measurement circuit, were obtained within the limitation of the first order leveling of the Geographical Survey Institute. However the measurement between BM 1029-BM 1030 was 0.6 mm out of the limitation. This was seemed to be caused by change of the field condition. There are two ponds named Midoriike and Kamome-ike between the two bench marks. Water overflowed from Kamome-ike to Midoriike during summer seasons in 1996 and 1997. Leveling survey had to be done in the water. This worst condition must be the reason of the measurement between BM 1029 and BM 1030 over the limitation. Except the results between BM 1029-BM 1030, no appreciable changes along the east-west direction (BM 1040-BM 1026) and the north-south direction (BM 1026-BM 1029) were observed for the last 15 years. It is inferred from geomorphological andgeophysical data that the crust around Syowa Station continues to uplift after deglaciation. The observations from repeat leveling measurements suggest no significant changes, which further supports the idea that the crustal uplift is a block movement. A route for repeat leveling survey was established around Syowa Station (69° S, 39° E), East Ongul Island, Antarctica in 1979 and 1982. The leveling measurements were repeated in 1996. However only 2.3 km out of the total length of 5.3 km route was surveyed for the time limitation during the summer operation of the 37th Japanese Antarctic Research Expedition (DARE-37). The other part of the route was measured by DARE-38 in February 1997. In total, the discrepancy of forwardand backward leveling, and closing error of the measurement circuit, were obtained within the limitation of the first order leveling of the Geographical Survey Institute. However the measurement between BM 1029-BM 1030 was 0.6 mm out of the limitation. This was seemed to be caused by change of the field condition. There are two ponds named Midoriike and Kamome-ike between the two bench marks. Water overflowed from Kamome-ike to Midoriike during summer seasons in 1996 and 1997. Leveling survey had to be done in the water. This worst condition must be the reason of the measurement between BM 1029 and BM 1030 over the limitation. Except the results between BM 1029-BM 1030, no appreciable changes along the east-west direction (BM 1040-BM 1026) and the north-south direction (BM 1026-BM 1029) were observed for the last 15 years. It is inferred from geomorphological and geophysical data that the crust around Syowa Station continues to uplift after deglaciation. The observations from repeat leveling measurements suggest no significant changes, which further sup-ports the idea that the crustal uplift is a block movement.