Study of Geoid Undulation in Southwestern Japan

1.为了精确确定日本西南部的大地水准面起伏，收集了重力测量、水准测量和潮汐观测数据以及卫星测高数据。2．使用WM102 GPS接收器对日本西南部的57个地点进行了GPS测量。 GPS 测量高度的平均重复性为 5.5 厘米。通过将GPS测量的椭球高差与目前水准测量获得的正高差进行比较，确定了这些点的大地水准面起伏差。 3．在鸟取、别府、纪伊和四国地区，使用 LaCoste & Romberg 重力仪进行了精确的重力测量。4。根据上述数据（1-3），获得了日本西南部大地水准面起伏差异等值线图。本研究确定的大地水准面差异与现有大地水准面（如ORI-89大地水准面）大致一致，但发现了数十厘米量级的系统差异。5． GPS/水准大地水准面起伏差异与迄今为止从 P 波走时分析获得的三维地震速度各向异性进行了比较。

1. In order to determine the geoid undulation precisely in the southwestern part of Japan, data obtained from gravity measurements, levelling surveys and tidal observations as well as satellite altimetry data have been collected.2. GPS measurements at 57 points in the southwestern part of Japan have been carried out with WM102 GPS receivers. Average repeatability of heights measured by GPS was 5.5 cm. Geoid undulation differences at these points have been determined by comparing ellipsoidal height differences measured by GPS with orthometric height ones so far obtained from levelling surveys.3. In Tottori, Beppu, Kii and Shikoku regions, precise gravity measurements were performed with LaCoste & Romberg gravimeters.4. Based on data mentioned above (1 - 3), a contour map of geoid undulation differences in the southwestern part of Japan was obtained. The geoid differences determined by the present study were approximately consistent with the proceeding geoids, such as the ORI-89 geoid, but systematic discrepancies of the order of a few ten centimeters were detected.5. GPS/levelling geoid undulation differences were compared with three-dimensional seismic velocity anisotropy so far obtained from P-wave travel-time analyses.