Gravity Change Detected by Repeated Absolute Gravity Measurements in Western Yunnan and Lhasa, China and Its Implication

Abstract

AbstractThe observational results of repeated absolute gravity measurements at the western Yunnan and Lhasa stations from 1990 are analyzed based on some new observations at these stations. Repeated observation results about 10 years at five stations in western Yunnan indicated that no significant gravity changes related to the geodynamical events were detected in most observational epochs. Significant gravity changes have been detected at Lijiang and Eryuan stations in western Yunnan before and after Lijiang earthquake (MS=7.0). We modeled the gravity changes caused by the co‐seismic dislocation during the Lijiang earthquake, that are in good agreement with the observed ones. The gravity changes with time in about 10 years at Lhasa station had a slope of –1.82±0.9×10−8m·s−2·a−1, indicate that Qinghai‐Xizang plateau has an uplift. The mechanisms of gravity changes at Lhasa were investigated. We calculated the gravity change rates based on the model of India plate to Eurasia subduction. The computed gravity change rate at Lhasa is in good agreement with observed one, that indicates the present gravity changes at Lhasa were caused by the India plate to Eurasia subduction. The Lhasa has an uplift rate of 8.7mm/a translated from gravity changes using computed ratio of the gravity changes to the vertical displacements from the dislocation model of the India plate to Eurasia subduction.