Present-day Tectonic Stress Field and GPS Observations in Hubei Province, Central China

Here, we show the present-day tectonic stress field and regional GPS velocity and strain rate fields in Hubei Province, central China. Our results are calculated based on the digital observation data from 01 January 2010, to 31 December 2017, by using the seis-CAP, P-wave first motion, and grid search methods and the software GAMIT/GLOBK10.4. The results show that the P axis azimuths of focal mechanism solutions, the principal compressional stress field, and the regional velocity and strain rate fields are conformably compressional in a NW–SE direction. The regional stress shape ratio R values are relatively low, and the faults are dominantly compressive-shear or compresso-shear faults. The average velocity modulus value for the GPS observation stations in western Hubei is 6.1 mm/a, which is higher than that in eastern Hubei (5.4 mm/a). The average velocity modulus value in the Jianghan Basin interior is relatively low (4.4 mm/a), while that in the northwestern Jianghan Basin is higher (7.6 mm/a). The strain rate field is characterized by NW–SE compression accompanied by NE–SW tension. The results suggest that the present-day crustal movement in Hubei Province is mainly controlled by collisions with the Indian Plate in the west and the Philippine Plate in the east and the consequent crustal shortening induced by western Hubei wedging into the Jianghan Basin. Further, the resistance by the thrust-and-fold belt in eastern Hubei contributes to the principal compressional movement in the study area. The T axis azimuth of focal mechanism solutions is consistent with the principal extensional stress field direction. In the central and northern Jianghan Basin, the R values are relatively high, the faults are mainly transtensional, and the crustal deformation is mainly extensional, which may be affected by the denudation, thinning and rapid rebound of the Dabie Orogen, resulting in tectonic extrusion and flow in the Jianghan Basin to both the NE and SW sides.