Objectives The Fenwei Basin is characterized by numerous tectonic faults, with the occurrence of many devastating earthquakes. Quantitatively studying the deformation difference between the Fenwei Basin and its adjacent blocks, and the impact of 2008 Wenchuan and 2011 Tohoku earthquakes will extend our understanding of present crustal movement characteristics of this region.
Methods We first used high precision global navigation satellite system (GNSS) velocities ranging from 2011 to 2017 to study the tectonic movement and relative activities of faults. Then the strain results were obtained by constructing a kinetic model using spherical least square collocation method to interpret differential strain characteristics among several blocks, followed by discussing the influence of different reference frames. Finally, the impact on deformation and seismic activities of neighboring large earthquakes was investigated by using both strain results and earthquake catalog.
Results (1) The Fenwei Basin and its neighboring blocks moves to SEE direction with reference to the stable Eurasian Plate, with the magnitude of approximate 5.18 mm/a and 1.54 mm/a in east and north components, respectively. Relative crustal motion rate between different blocks was approximate 1-2 mm/a. (2) The whole area exhibited NW-SE oriented principal extensional strain and the role of accommodation zone that the Fenwei Basin plays in differential movement within peripheral blocks was well revealed by typical domain profile results. (3) The maximum shear strain rate decreased after the Wenchuan and Tohoku earthquakes, and the seismic activities dropped after the Tohoku earthquake.
Conclusions Our study suggested notable deformation differences between the Fenwei Basin and its adjacent blocks. The tectonic strain accumulation process in the Fenwei Basin decelerated due to co-seismic and post-seismic effect of the two great earthquakes.