Inversion of GPS measurements for a layer of negative dislocation distribution in north China

Abstract

In north China, most earthquakes occur at depths of 10–25 km and are considered to be the direct result of deformation or rupture of the brittle upper crustal layer. To describe this mechanism, a planar horizontal negative dislocation plane is used to represent the force of action of the lower crustal layer on an overlying brittle upper crust layer. An area around Beijing in north China has been chosen for applying this negative dislocation layer assumption. A GPS network (Capital Circle GPS Network, CCGN), has been set up for monitoring crust deformations since 1992. In this paper, observations from 1992, 1995, and 1996 GPS surveying campaigns were used to determine model parameters of a negative dislocation layer. Using a Bayesian inversion procedure, more than 95% of data residuals are found to be <2 mm/yr, indicating that the negative dislocation layer model can fit GPS data well. The inversion results show that the local tectonic movement is −2 ± 1 mm/yr in the north and 7 ± 1 mm/yr in the east, and the high negative dislocation rates occur mainly in the south part of the north Taihang mountain zone with a magnitude of ∼4 ± 1 mm/yr, and the east part of the Yan mountain zone with a magnitude of ∼3 ± 1 mm/yr. By applying this negative dislocation layer model, the continuous GPS surveying data can be inverted to determine the negative dislocation rate distributions in the middle or upper seismogenic crust layer, so as to predict the locations of potential earthquake sources.