Crustal deformation before the 2008 Wenchuan MS8.0 earthquake studied using GPS data

Qiang Li, Zhenyu Zou, Long Zhang, Qi Liu, Wenxin Wei, Zaisen Jiang, Jing Zhao, Xiaoxia Liu, & Yanqiang Wu

Published April 2015, SCEC Contribution #6747

We used GPS velocities from approximately 700 stations in western China to study the crustal deforma-tion before the Wenchuan MS8.0 earthquake. The processing methods included analyses of the strain ratefield, inversion of fault locking and the GPS velocity profiles. The GPS strain rate in the E-W direction in theQinghai-Tibet block shows that extensional deformation was dominant in the western region of the block(west of 92.5◦E), while compressive deformation predominated in the eastern region of the block (from92.5◦E to 100◦E). On a regional scale, the hypocentral region of the Wenchuan earthquake was locatedat the edge of an intense compression deformation zone of about 1.9 × 10−8/a in an east-west direction.The characteristic deformation in the seismogenic fault was compressive with a dextral component. Thecompression deformation rate was greater in the fault’s western region than in its eastern region, and thestrain accumulation was very slow on the fault scale. The results of a fault locking inversion show thatthe locking fraction and slip deficit was greater in the middle-northern section of the seismogenic faultthan in the southern section. The GPS velocity profile before the Wenchuan earthquake shows that thecompression deformation was smaller than the dextral deformation, which is asymmetrical with respectto the distribution of co-seismic displacement. These deformation characteristics should provide someclues to the Wenchuan earthquake which occurred in the later period of the earthquake cycle.

Li, Q., Zou, Z., Zhang, L., Liu, Q., Wei, W., Jiang, Z., Zhao, J., Liu, X., & Wu, Y. (2015). Crustal deformation before the 2008 Wenchuan MS8.0 earthquake studied using GPS data. Journal of Geodynamics, 85, 11-23. doi: 10.1016/j.jog.2014.12.002.