Abstract
As one of members of the Seismological Mission to the People's Republic of China, the author has the opportunity to contact with Chinese researchers for gravity change. In China, repeated gravity measurements have been made for monitoring preseismic changes in gravity since the 1966 Xingtai earthquake . The purpose of this paper is to introduce the gravity-change results obtained for the 1975 Haicheng, the 1976 Songpan Pingwu and the 1976 Tangshan earthquakes. Inf ormations concerning with the Songpan Pingwu earthquake have not so much been given outside China . The gravity change there has the general tendency to appear in the extensive areas surrounding the epicenter. The preseismic gravity change is sometimes found even in areas of 200 km distant from the epicenter. Another feature is that the maximum change amounts to a few hundred?Egals, sometimes ten times larger than what is expected from free-air rate. Possible cause of such a large and wide change lies in the fact that the continental crust is geologically uniform with large-scale faults . In order to check instrumental differences, if any, the mutual field comparison should be made between worldwidely-used LaCoste and Romberg gravimeters and the gravimeters used in China.
