华北平原沉降地区重力场变化分析

AN ANALYSIS OF GRAVTY FIELD VARIATION IN THE SUBSIDENCE AREA OF NORTH CHINA PLAIN

华北平原沉降带相对于西部太行山区,近几年观测到的重力值相对1989年同期呈上升状态、其中某些地区累计上升量相当大,比如,沧州地区达143×10^(-8)m/s^2,任丘地区103×10^(-8)m/s^2,巨鹿—南宫为(89—103)×10^(-8)m/s^2.对某些地区的重力变化量进行地下水下降量和地面沉降量校正,其校正量可达到变化量的1/3—1/2.校正后的重力值变化幅度减小,但有些异常依然存在.这种较大的剩余变化量,可能含有两个因素:其一可能与华北平原沉降带的继承性下降及某些地区构造断裂活动有关;其二可能是实际地面沉降量比推测的沉降量大.

In recent several years,the observed gravity values in the subsidence zone in North China plain have showed rising state compared with that of the same operiod of 1989 and with that in the western Tai-hang mountain area, the accumulated rising quantity in some areas is quite large, for example, it has reached 143× 10-8m/s2 in Cangzhou region, 103×10-8m/s2in Renqiu region,89-103×10-8m/s2in Julu - Nangong region. The correction of groundwater decending quantity and ground subsidence quantityhas been made for the varied gravity quantity in some regions, its corrected quantity made up 1/3-1/2of the varied quantity. After correction, the variational amplitude of gravity values decreased, but some anomalies still existed. Such a relatively large residue variational quantity may contain two factors: one is possibly related with the inherited subsidence of subsidence zone of North China plain and with the structural fault activity in some areas; the other is possibly that the actual ground subsidence quantity is larger than the inferred subsidence quantity.