Crustal deformation and strain fields of the Weihe Basin and surrounding area of central China based on GPS observations and kinematic models

The Weihe Basin in central China is characterized by its complex geological background and intense tectonic activity. This study examined the characteristics of the crustal deformation and strain field of the Weihe Basin and its surroundings based on campaign Global Positioning System (GPS) data acquired during 2001-2011. We first analyzed the variations of crustal movement and we calculated the crustal strain rates by establishing sound strain models. Both the characteristics of the strain field and the correlation between the maximum shear strain field and the distribution of seismicity were investigated. Our results indicated that the overall crustal movement of the Weihe Basin region was temporally continuous during 2001-2011, despite short-term fluctuation during 2007-2008. We found that western and eastern parts of the Weihe Basin region presented considerably different tectonic characteristics with predominantly compressional strain in the west and extensional strain in the east. However, the magnitude and direction of the overall crustal movement, and the relative differential motions of the Weihe Basin region, changed obviously during 2007-2008 with substantially increased compressional strain in western areas. We conclude that regions with higher shear strain are also those with frequent earthquakes, the distribution of which might have been affected by the M8.0 Wenchuan earthquake in May 2008. According to variations of the crustal deformation and the strain field, we further infer that western parts of the Weihe Basin region during 2007-2008 might have been affected by a northeastward extrusion caused by the Wenchuan earthquake. However, this dynamic effect might have gradually permeated to eastern parts of the Weihe Basin region during 2008-2011. The results obtained in this paper not only portray the current tectonic activity deformations but also the recent geodynamic processes of the Weihe Basin and its surrounding area.