Gravity Anomalies in East Nepal and their Implications to the Crustal Structure of the Himalayas

Gravity measurements were carried out at 145 points in eastern Nepal as a part of the scientific programme of the Japanese Mount Everest Expedition 1970. As the position and elevation of the gravity stations were determined by maps with the aid of an aneroid altimeter, they have standard errors of about 400 m and 33 m, respectively. Correspondingly, the gravity anomalies presented in this paper have errors of 5–15 mgal. Free-air, Bouguer, Pratt–Hayford and Airy–Heiskanen anomalies were obtained from these data. A terrain correction of Hayford zones F–O was applied in the calculation of the latter three anomalies. The terrain correction amounts to more than 40 mgal at many stations. The gravity data were divided into three groups according to geological-morphological zones of east Nepal; (a) Higher Himalayas, (b) Lower Himalayas, and (c) Foothills.