Crustal gravitational energy change caused by earthquakes in Tibet

Earthquakes not only release seismic-wave energy, which decays eventually, but also generate permanent deformations in the Earth. This permanent deformation causes gravitational potential energy (GPE) change. The GPE change is as large as three to four orders of magnitude greater than the released seismic-wave energy. Previous researches showed that the GPE change is a good indicator of extensional and compressional tectonics. In this paper, we first propose a new method to calculate GPE change based on the point dislocation theory for a SNREI Earth. This method makes the companying computations simpler in that the integration of vertical displacement in crust degenerates to a difference of two values of a function at crust’s boundaries. Then we investigate the GPE change caused by earthquakes from 1976 to 2013 in Tibet extracted from GCMT (global centroid moment tensor) catalogue. The cumulative GPE change due to earthquakes in Tibet shows that in the central and western parts of Tibetan plateau GPE decreased more from 1999 to 2013 than from 1976 to 1998 while in the eastern part GPE increased more, which reflect more rapid extensional and compressional tectonic environments, respectively. In addition, in the neighboring areas, some obvious tectonic-correlated GPE gain and loss are also shown.