Gravity variation in the Tibet area before the Nepal Ms8.1 earthquake

This research utilized two periods of gravity monitoring results from 2010 to 2013 from the Continental Tectonics Environmental Monitoring Network of China, analyzed the correlation between gravity variation in the Tibet area and the Nepal Ms8.1 earthquake, and investigated the gravity variation mechanism in combination with the crust vertical movement and horizontal strain field observed by Global Positioning System (GPS). The research results indicated that (1) the gravity variation exhibited apparent characteristics of a positive anomaly and high gradient zone in the Himalayan frontier. This observation is consistent with the existing recognition of the gravity anomaly and occurrence regularity of a strong earthquake; (2) the gravity variation exhibited apparent consistence with the spacious distribution of the vertical movement and the horizontal deformation field in that area. The crustal vertical movement was not the direct cause leading to the gravity variation. It is assumed that the crust stress-strain accumulation in the Qinghai-Tibetan Plateau and its adjacent areas is the important factor that resulted in the variation of gravity.