???????????????????????????仯

??????????????????????????????????仯??????????????????????????仯?????????λ?仯?????????????????????????????????????????????????????????仯?????????????????????????С?????????????ε??????仯????й??????????????????????????????????????????????????????????????????????????????????????仯????????

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

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.