Dizhi lixue xuebao (Apr 2021)

Estimation of displacements along strike-slip fault on a million-year timescale: A case study of the AltynTagh fault system

  • HUANG Feipeng,
  • ZHANG Huiping,
  • XIONG Jianguo,
  • ZHAO Xudong

DOI
https://doi.org/10.12090/j.issn.1006-6616.2021.27.02.020
Journal volume & issue
Vol. 27, no. 2
pp. 208 – 217

Abstract

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Fault slip rate matters not only as one of the important parameters for quantitative study of Cenozoic tectonics but also a key element in geodynamic research. However, most studies have focused on the long-term (>Ma) cumulative displacement of geological mass, short-time (since the late Quaternary) dislocation of geomorphic units as well as annual-decadal geodetic observations, and few people studied the fault displacement on a timescale in between, leaving a gap in understanding the evolutionary history of fault on a million-year timescale. Since the strike-slip fault breaks the system of alluvial fans and their catchment basins, causing the spatially uneven distribution of residual offset alluvial fans along the fault direction, we proposed three methods to determine the large-scale cumulative displacement of strike-slip fault based on the offset alluvial fans. The first method commonly presents a correspondence between the alluvial-fan area and catchment basin area as Af=γAc(Af is the alluvial-fan area, Ac is the catchment basin area, γ is a constant 0.5±0.35), which leads us to determine the strike-slip displacement of the offset basin by identifying whether the correspondence is unusual. The second method helps us to get the strike-slip displacement by distinguishing geomorphic units with the same lithological mineral components distributed at both sides of the fault. The third is to measure the strike-slip displacement by comparing the residual geomorphic unit with the corresponding stream outlet. In this study, we applied the above three methods to study the strike-slip displacement of the AltynTagh fault system on a million-year timescale, and to estimate the formation age of these geomorphic units based on the exiting fault slip-rate. It is further verified that the estimation methods proposed in this paper can provide a new angle and technical solution to accurately determine the evolution history of the strike-slip fault on a million-year scale.

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