陆态网络绝对重力基准的建立及应用

利用陆态网络100个基准站的首期观测数据,建立了基本覆盖我国大陆范围的高精度绝对重力基准,各基准站点值精度均小于5.0μGal/a,为相对重力联测提供了高精度起算基准点,可获得真实的相对重力联测平差结果,避免重复重力观测获得的重力场动态变化图出现畸变。成都基准台重复重力观测获得的重力变化规律表明,汶川地震前长期重力变化率达5.01±0.7μGal/a,如此大的震前重力变化很可能是由于地下物质运移引起的。联合绝对重力和GRACE卫星长期测量数据,根据二者系统偏差确定了武汉地区的地壳沉降速率,为-3.27±0.65mm/a。

Establishment of Absolute Gravity Datum in CMONOC and Its Application

The high accuracy absolute gravity datum covered the Chinese mainland area is established by using absolute gravity measurement data of one hundred stations in CMONOC (Crustal Movement Observation Network of China),the accuracy of each station is better than 5.0μGal/a .The high accuracy gravity datum can be used for relative gravity measurements in adjustment,and the real gravity value can be determined from relative gravity measurement data of adjustment by using the gravity datum to avoid distortion of the real figure of gravity change.The trend of absolute gravity change from several observations at Chengdu station shows that the secular trend of gravity change is larger than 5.01 ±0.7μGal/a ,which is probably caused by the distribution of mass below the earth.The rate of land subsidence of Wuhan area is 3.27±0.65 mm/a determined from combined long-term absolute gravity measurements and GRACE satellite data according to the two system difference.