The 2016 Mw 6.0 Hutubi earthquake: A blind thrust event along the northern Tian Shan front

Abstract The Tian Shan Range, which trends E-W along the southern margin of the Junggar Basin, is one of the longest and most active intracontinental orogenic belts in central Asia. On 8 December 2016 (05:15:04 UTC), a Mw 6.0 earthquake ruptured the northern Tian Shan front. Here, we use Sentinel-1 radar imagery to investigate the deformation and source parameters related to this event. The co-seismic surface deformation was predominated by uplift without surface rupture. Ascending and descending interferograms indicate that the event triggered small co-seismic deformations with maximum line-of-sight displacements of 22 mm and 24 mm, respectively. Although the north-dipping and south-dipping plane solutions can both fit the observations well, the north-dipping solution with a dip of 58° is preferred in consideration of the relocated aftershocks and regional geological structure. Significant slip is located between depths of 12 km and 17 km, suggesting that the event was caused by a completely blind thrust fault. This blind rupture is characterized largely by a compact thrusting patch with a peak slip of 56 cm at a depth of 13 km. The source model generates a geodetic moment of 6.678 × 10 17  N m corresponding to a Mw 5.85 event. Both the interferometric synthetic aperture radar modeling and the aftershock locations indicate that the rupture plane is linked to the Huoerguosi-Manas-Tugulu fault at a depth of ∼16 km, a typical locking depth in the Tian Shan. We suggest that the 2016 Hutubi earthquake more likely occurred on a back-thrust of the Huoerguosi-Manas-Tugulu fault, and the back-thrust is interpreted to represent a preexisting normal fault beneath the Qigu anticline belt that was tectonically inverted during the Cenozoic.