Evidence of paleoearthquakes from trench investigations along Pinjore Garden fault in Pinjore Dun, NW Himalaya

Journal of Earth system science

Javed N Malik1²  George Mathew2¹ 

[1] Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai 400 076.$$;Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016.$$

关键词: Pinjore;    Himalaya;    active faults;    paleoearthquakes;    trench.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

The Pinjore Garden Fault (PGF) striking NNW–SSE is now considered one of the active faults displacing the younger Quaternary surfaces in the piggyback basin of Pinjore Dun. This has displaced the older Kalka and Pinjore surfaces, along with the other younger surfaces giving rise to WSW and SW-facing fault scarps with heights ranging from 2 to 16m. The PGF represents a younger branch of the Main Boundary Thrust (MBT) system. An ∼4m wide trench excavated across the PGF has revealed displacement of younger Quaternary deposits along a low angle thrust fault. Either side of the trench-walls reveals contrasting slip-related deformation of lithounits. The northern wall shows displacement of lithounits along a low-angle thrust fault, while the southern wall shows well-developed fault-related folding of thick sand unit. The sudden change in the deformational features on the southern wall is an evidence of the changing fault geometry within a short distance. Out of five prominent lithounits identified in the trench, the lower four units show displacement along a single fault. The basal unit ‘A’ shows maximum displacement of about To = 2.85 m, unit B = 1.8m and unit C = 1.45 m. The displacement measured between the sedimentary units and retro-deformation of trench log suggests that at least two earthquake events have occurred along the PGF. The units A and D mark the event horizons. Considering the average amount of displacement during one single event (2m) and the minimum length of the fault trace (∼45 km), the behaviour of PGF seems similar to that of the Himalayan Frontal Fault (HFF) and appears capable of producing large magnitude earthquakes.

【 授权许可】

Unknown