Blind thrust rupture of the 2015 Mw 6.4 Pishan earthquake in the Northwest Tibetan Plateau by joint inversion of InSAR and seismic data

Abstract The July 3rd, 2015 Pishan, China Mw 6.4 earthquake occurred within the Hetian fold belt, a frontal thrust region between the Northwestern Tibetan Plateau and the Tarim basin. We investigate the fault geometry and the rupture process of the Pishan earthquake based on joint inversion of teleseismic body waves and InSAR measurements. Our results show that the top of the fault that ruptured in the Pishan earthquake is buried 5 ± 2 km beneath the surface and that the earthquake ruptured only a segment of a deeply-seated detachment lying under the Hetian fold belt. Our inferred coseismic slip model shows two slip asperities, located in the depth range of about 7–9 km and 10–11 km. Additionally, we resolve a slip deficit region between the slip asperities, which might indicate friction heterogeneity on the fault plane. The earthquake ruptured for ∼15 s, releasing a total seismic moment of 4.7 × 10 18  N m. We also show that the latest Pishan earthquake caused positive Coulomb stress changes on back thrust faults, potentially decreasing the time to the next earthquake on those faults. Based on our Pishan coseismic slip model, along with both the trend of the anticline system and the pattern of coseismic deformation, we envision an ongoing east-west extensional growth of the anticlines in the Western Kunlun frontal thrust region in addition to the northern underthrusting of the Northwestern Tibetan Plateau below the Tarim basin.

[1]  Peizhen Zhang,et al.  Present‐day crustal motion within the Tibetan Plateau inferred from GPS measurements , 2007 .

[2]  Jie Chen,et al.  The 2015 Mw 6.4 Pishan Earthquake: Seismic Hazards of an Active Blind Wedge Thrust System at the Western Kunlun Range Front, Northwest Tibetan Plateau , 2016 .

[3]  Jian Lin,et al.  Stress triggering in thrust and subduction earthquakes and stress interaction between the southern San Andreas and nearby thrust and strike-slip faults , 2004 .

[4]  Triggered slip on a back reverse fault in the Mw6.8 2013 Lushan, China earthquake revealed by joint inversion of local strong motion accelerograms and geodetic measurements , 2016 .

[5]  Walter H. F. Smith,et al.  New, improved version of generic mapping tools released , 1998 .

[6]  Kaihua Ding,et al.  Source model of the 2015 Mw 6.4 Pishan earthquake constrained by interferometric synthetic aperture radar and GPS: Insight into blind rupture in the western Kunlun Shan , 2016 .

[7]  Keiiti Aki,et al.  Fault plane with barriers: A versatile earthquake model , 1977 .

[8]  T. Wright,et al.  Toward mapping surface deformation in three dimensions using InSAR , 2004 .

[9]  Y. Okada.  Surface deformation due to shear and tensile faults in a half-space , 1985 .

[10]  X. Shan,et al.  Slip in the 2015 Mw 7.9 Gorkha and Mw 7.3 Kodari, Nepal, Earthquakes Revealed by Seismic and Geodetic Data: Delayed Slip in the Gorkha and Slip Deficit between the Two Earthquakes , 2015 .

[11]  Xiaodian Jiang,et al.  Seismic reflection data support episodic and simultaneous growth of the Tibetan Plateau since 25 Myr , 2014, Nature Communications.

[12]  Allen H. Olson,et al.  Finite faults and inverse theory with applications to the 1979 Imperial Valley earthquake , 1982 .

[13]  Paul Lundgren,et al.  Joint Inversion of InSAR, GPS, Teleseismic, and Strong-Motion Data for the Spatial and Temporal Distribution of Earthquake Slip: Application to the 1999 İzmit Mainshock , 2002 .

[14]  Serkan B. Bozkurt,et al.  Forecasting the evolution of seismicity in southern California : Animations built on earthquake stress transfer : Stress transfer, earthquake triggering, and time-dependent seismic hazard , 2005 .

[15]  Hiroo Kanamori,et al.  Seismological aspects of the Guatemala Earthquake of February 4, 1976 , 1978 .

[16]  M. Vallée,et al.  Evidence of sudden rupture of a large asperity during the 2008 Mw7.9 Wenchuan earthquake based on strong motion analysis , 2012 .

[17]  Guangcai Feng,et al.  Geodetic model of the 2015 April 25 Mw 7.8 Gorkha Nepal Earthquake and Mw 7.3 aftershock estimated from InSAR and GPS data , 2015 .