Comparisons between variations of the vertical and the long term variations of the tilt are made for the period of the 1987-1988 El Nino event. Variations of the vertical are derived from astronomical observations of latitude and time at Mizusawa . The tilt observations are derived from water tube tiltmeters at the Esashi Earth Tides Station. We have (1 year running mean) -(4 year running mean) for both data. It is found a relation between deflection of the vertical toward the north and the N-down of the tiltmeter in the north-south component and deflection of the vertical toward the west and the E-up of the tiltmeter in the east -west component. The equatorial waves in the ocean contribute to variations of the vertical as waves of density variation progressing as waves. At a station near the sea coast the effect of the density waves can be observed in variations of the vertical and the tilt, provided that the equatorial waves contribute to excitation of the Rossby waves in the mid-latitude in the Pacific Ocean. The El Nino events couple with changes of the speed of the Earth rotation . Variations of the centrifugal potential due to changes of the Earth rotation induce changes of the zonal flows in the North Pacific Ocean and cause the meridional gradient of the zonal flows, which can give the triggering mechanism for excitation of off-equatorial Rossby waves in the mid-latitude in the Pacific Ocean.

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Since 1994 Geographical Survey Institute, Japan has deployed the GPS system (GEONET) which is composed of about 890 sites, and covers Japan Islands with interval length of about 25 km . This system is very powerful to detect the movement ofJapan Islands. However, it is difficult to detect the local crustal movement caused by volcanic and/or tectonic activity by GEONET, whose dimension is several 10 km. We need more dense GPS network to detect local events. Recently, a new small L1GPS receiver has been developed, which is improved for car navigation system. This type of receiver is small and cheep, and phase data can be generated. It may be useful for realizing the more dense GPS network and portable GPS System . Test measurements were carried out to verify that crustal deformation can be detected with the receivers. 5 baselines with length between 0.5 and 6 km were measured and Bernese GPS SoftwareVer 4.0 is used for the baseline analysis . The repeatabilities of length and height are 3 mm and 6.5 mm for 6 km baseline when the session length is 1 hour and the sampling interval is 1 second . Repeatabilities of length and height are 4 mm and 9 mm for 5 km baseline when session length is 40 minutes and sampling interval is 30 second. It has enough resolution to detect local crustal movement. It proves the possibility to realize the dense GPS network and portable GPS System using the small L1 GPS receiver.

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Modern geodetic coordinate systems and their transformations are studied and solutions to various problems in this field are presented. For example, we proposed that WGS-84 coordinate system and WGS-84 ellipsoid should not be used any more for precise measurements.

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Methods to translate geoidal heights from a certain coordinate system to an arbitrary system with the corresponding ellipsoid are studied. We propose a simple method, which ignores the errors due to the difference in normals of two ellipsoids, for general users of grid data of geoidal heights. The simple method is easy to understand, and reducesmistakes and loads to computers in calculation. Moreover the errors are very small compared to those of grid geoidal heights. I adopted this method and developed a software "jgeoidtrn 97 for Windows 95", which enables users to calculate geoidal heights in their coordinate systems with ellipsoids, such as ITRF 94 with GRS-80, WGS-84 with WGS-84, and Tokyo 97 coordinate system with Bessel ellipsoid.

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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.

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Vertical crustal movement in the area near the Kouzu-Matsuda fault zone associated with the 1923 Kanto Earthquake is investigated through detail profile of the movement on the leveling line crossing the fault zone. On the, hanging side of thefault, the uplift is 2 m on the bench mark nearest to the fault line, then the uplift decreases gradually with the distance from the fault and amount to about 40 cm at the distance of 30 km. On foot side of the fault, the maximum uplift is 1.8 m just near the fault line and decreases sharply with the distance and reaches about 20 cm at the distance of 10 km from the fault. This pattern of vertical movement is harmonious with the horizontal movement in the focal area and suggest the movement of the Kouzu-Matsuda fault system at the time of 1923 earthquake, though additional minor earthquake faults might be necessary to explain the uplift of the foot side.

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