Cryptic Faults, Seismic Hazards and Lithospheric Controls on Crustal Reactivation in the Gobi Corridor Region, Central Asia

Session: Cryptic Faults: Assessing Seismic Hazard on Slow Slipping, Blind or Distributed Fault Systems
Type: Oral
Date: 4/28/2020
Time: 05:15 PM
Room: 240
Description: 

The active deformation field between northern Tibet and central Mongolia is dominated by diffuse sinistral transpressional reactivation of the southern Altaids Phanerozoic terrane collage. The angular relationship between NE-directed SHmax and pre-existing basement trends is the dominant control on Quaternary fault kinematics. The availability of high-resolution digital imagery coupled with 20 years of field verification has led to the identification of many previously undiscovered cryptic faults that pose a potential earthquake hazard. The active fault array indicates that transpressional duplexing is a previously unrecognized but important mechanism of crustal reactivation, strain transfer and mountain building. In the north Tibetan Foreland, uplift and northward expansion of the northernmost plateau in the Nanjieshan and Sanweishan region occurs by sinistral oblique-slip thrust ridge development within a regional asymmetric flower structure centered on the Altyn Tagh Fault. In the southern Beishan, interconnected lensoidal domains of transpressional and transtensional faulting are subtly indicated by Quaternary fault scarps, low-relief rejuvenated landscapes and alluvial sedimentation. The SE Beishan and western Hexi Corridor region contains numerous previously unrecognized Late Quaternary fault scarps that indicate structural and kinematic connectivity between the Helishan-Longshoushan fault array and the transtensional grabens of the Yabrai and Langshan in the eastern Alxa Block. Active faulting in the Harlik Tagh restraining bend of the easternmost Tien Shan represents the terminal accommodation zone for the 800km-long Gobi-Tien Shan sinistral fault array in SW and S Mongolia. The historical earthquake record and regional distribution of Quaternary fault scarps throughout the Gobi Corridor region suggests that tectonic loading is shared amongst a diffuse fault network challenging assumptions about earthquake recurrence intervals and seismic hazard forecasting in intraplate continental interior settings.

Presenting Author: Dickson Cunningham

Authors