Long-Term Gravity Changes in Tibet and Its Vicinity before the Nepal Ms8.1 Earthquake
1 Key Laboratory of Earthquake Geodesy, Institute of Seismology, CEA, 40 Hongshance Road, Wuhan 430071, China
2 Wuhan Base of Institute of Crustal Dynamics, CEA, 40 Hongshance Road, Wuhan 430071, China
Abstract:Using measurements from three national repeated gravity networks-the crustal movement observation network of ChinaⅠ, digital earthquake observation network of China, and the crustal movement observation network of China during 1998-2013, we obtain the annual gravity rate in Tibet and
its vicinity. Based on the lake level change in Qinghai-Tibet Plateau, we estimate the gravity effects due to the continental water storage changes at each site. Finally, we obtain the spatial distribution of the long-term gravity changes in Tibet and its vicinity through spatial Gaussian filter with 50 km smooth radius. From our research we find: 1) The time series at typical gravity stations show a clear linear trend, which means the linear trend is the principal characteristic at those stations. The positive linear trend implies accumulated regional gravity changes in the past decades. 2) The long-term gravity changes in Tibet and its vicinity show uneven spatial distribution, which might be related with the complicated crustal deformation and geodynamical mechanisms in the Qinghai-Tibet Plateau. The Himalayan tectonic block shows a significant positive gravity annual rate, which might be related to underground mass redistribution and adjustment caused by continuous extrusional deformation between the Indian and the Eurasian plates. The positive gravity variations might indicate the stress and energy acceleration surrounding the locality of the earthquake due to the crustal deformation and medium changes during the process of earthquake preparation.
KANG Kaixuan,LI Hui,LIU Shaoming et al. Long-Term Gravity Changes in Tibet and Its Vicinity before the Nepal Ms8.1 Earthquake[J]. jgg, 2015, 35(5): 742-746.