三峡坝区二次蓄水前后的局部重力场变化

CHANGES OF LOCAL GRAVITY FIELD BEFORE AND AFTER SECOND IMPOUNDMENT IN THREE GORGES DAM AREA

通过分析三峡坝区二次蓄水前后局部重力场的变化特征发现:二次蓄水后的重力场变化与相应的库水位变化基本吻合,但在坝前区域与首次蓄水相比差异明显,水库南北两侧极不对称,北侧变化幅度大、衰减较慢;南侧则增幅较小、衰减很快;香溪库段的重力变化比较有规律,基本上以长江为轴对称展开,并呈现出南侧强于北侧的特点。观测结果再次证实:三峡水库二次蓄水后,香溪库段仍是重力变化最大的区域。

By analyzing the characteristics of gravity changes before and after the second impoundment in the Three Gorges dam area, we have found that the variation of gravity approximately accords with the change of water level in the Three Gorges reservoir, but in the head area of reservoir, the difference between the change relations of gravity to water level under the first and the second impoundment is obvious. The gravity changes by the south and north sides in the head area is extremely dissymmetric. The gravity field by the north side changes greatly and attenuates slowly, while that by south side has smaller changes and attenuates quick. In the Xiangxi segment, the variation of gravity is quite regular and presents the characteristics that the gravity changes is stronger by the south side than that by the north side taking basically the Yangtz river as the axis of symmetry. The observation results confirm that the maximum gravity change is still in Xiangxi segment after second impoundment.