利用TWVD2001水準資料推估臺灣地區高程變動速度場之研究

Estimation of Taiwan Vertical Velocity Field Using TWVD2001 Leveling Data

臺灣最精確的垂直基準—臺灣高程基準（Taiwan Vertical Datum 2001,TWVD2001）於2000年至2003年間以精密水準測量技術建置完成，包含一等一級與一等二級水準網，總計2065個一等水準點。然而，TWVD2001建置至今已接近十年，其間實施了數次精密水準重測工作。本文的目的即為結合2000年至2008年間所蒐集的一等水準測量資料，以帶有速度量參數之最小二乘估計法（Least-Squares Estimation, LSE）求解各一等水準點的平均高程變動速度量，並利用各點位的變動速度值以最小曲率法內插獲得高程變動速度場。本文共獲得3項結論：（1）水準點高程變動速度的平均精度為±0.164 cm/yr；（2）在99.9%信心區間之統計測試下，有785個點位的高程變動速度是顯著的；（3）由臺灣地區的高程變動速度場顯示：彰化、雲林、嘉義、屏東、宜蘭地區為地勢沉陷區，並以雲林縣的沉陷最顯著，最大-9.83 cm/yr，平均-3.65 cm/yr，而中央山脈、海岸山脈為抬升區，抬升速度最大者位於花蓮縣，達2.94 cm/yr。本文的結果與中央地質調查所之全島GPS估計結果大致吻合。由於精密水準測量為獲取正高最精確的測量方法，故本研究的成果對於臺灣高程變動之進一步探討扮演重要的角色。 Taiwan Vertical Datum 2001 (TWVD2001), the most precise vertical datum in Taiwan, was established by precise geodetic leveling technique from 2000 to 2003, consisting of 2065 benchmarks sited on the first-order first-class and the first-order second-class leveling networks. To date, however, the TWVD2001 has been set up for almost ten years ago. During this period, sever al precise geodetic leveling surveys along the first-order leveling lines were finished. The aim of this paper is to combine those first-order leveling data collected from 2000 to 2008 to estimate the average vertical rate of each benchmark by least-squares estimation (LSE) with the additions of vertical rate parameter. Furthermore, the velocity field is interpolated by the minimum curvature method using the estimated vertical rates of each first-order benchmark. Tree conclusions of this study has obtained as follows：(1) The average accuracy of the all vertical rates is ±0.164 cm/yr. (2) Based on the statistic tests of 99.9% confidence interval, 785 vertical rates of benchmark are significant. (3) From the estimations of Taiwan vertical velocity field, Zhanghua, Yunlin, Jiayi, Bingdong and Yilan are land subsidence areas. Especially, Yunlin appears to be the most severe land subsidence area which average sinking rate is -3.65 cm/yr and the largest one is -9.83 cm/yr. The Central Range and Coastal Range are the rising area. The largest uplifting rate is in Hwalien with 2.94 cm/yr. The results of this study are consonant with the island-wide GPS results obtained from the Central Geological Survey. Because the leveling technique is the most precise technique for determining the orthometric height, the results of this study will play an important role in the further research of land vertical displacement in Taiwan.