蓟县基准站长期重力变化特征研究

Characteristics of Long-Term Gravity Variation at Jixian Datum Station

基于蓟县GNSS基准站1998~2018年近20 a的绝对重力长期变化资料,联合地面大地测量(绝对重力、GNSS)、地表及地下水文数据和GRACE卫星重力数据,计算并分析由地表垂直位移、地下水及地表水负荷等不同物理信号产生的重力效应,获取各影响因素的长期重力变化特征,并对结果进行深入分析研究,得出以下结论:1)蓟县基准站绝对重力近20 a的长期变化总体呈下降趋势,变化率为-1.64±0.53μGal/a;2)2004~2017年井水位数据显示,蓟县GNSS基准站所在地区地下水水位呈现明显的下降趋势,变化率为-0.66±0.07 m/a,产生的重力效应为-1.94±0.22μGal/a,是影响该点重力变化的最主要因素;3)综合分析蓟县基准站地面绝对重力和其他各因素重力效应的长期变化特征认为,该点存在每年0.43±0.58μGal的重力上升变化,可能与首都圈地区上地幔顶部高密度物质的上涌有一定关系。

We combine ground geodetic data(absolute gravity,GNSS),surface and underground hydrological data,and GRACE satellite gravity data.Based on the long-term variation of absolute gravity at Jixian GNSS datum station in 20 recent years(1998 to 2018),we calculate and analyze the gravity effect caused by different physical signals,including the vertical displacement of the earth’s surface,groundwater and surface water load.Then,the characteristics of long-term gravity variation of each influencing factor are obtained,and the following conclusions are drawn through in-depth analysis and study:The long-term variation of absolute gravity at Jixian datum station from 1998 to 2018 shows a downward trend as a whole,and the change rate is about-1.64±0.53μGal/a.The well water level data from 2004 to 2017 shows that the groundwater at Jixian GNSS datum station has an obvious downward trend,with a change rate of about-0.66±0.07 m/a,and the gravity effect is-1.94±0.22μGal/a.It is the most important factor that affects the gravity change of this point.A comprehensive analysis of the long-term variation characteristics of the ground absolute gravity and other gravity effect factors shows that there is a gravity rise of about 0.43±0.58μGal/a at Jixian datum station.It may be related to the upwelling of high-density matter at the top of the upper mantle in the capital circle area.