Analysis of datum-instability effect on calculated results of data from Longmen Mountain regional gravity network

:A statistical correlation method is used to study the effect of instability of the calculation datum (used in traditional method of indirect adjustment) on calculated gravity results, using data recorded by Long-men Mountain regional gravity network during 1996 – 2007. The result shows that when this effect is corrected, anomalous gravity changes before the 2008 Wenchuan Ms8.0 earthquake become obvious and characteristically distinctive. Thus the datum-stability problem must be considered when processing and analyzing data recorded by a regional gravity network.