走滑断裂百万年时间尺度位移量估计及其在阿尔金断裂系中的应用

断裂滑动速率不仅是新生代构造定量研究的重要参数之一,也是地球动力学研究的重要组成部分.但现有研究普遍缺乏介于长时间尺度(>Ma)地质体累积位移和短时间尺度(晚第四纪以来)地貌单元位错以及年—十年尺度的大地测量观测之间的断裂位移量,从而造成了理解百万年时间尺度下断裂演化历史的空区.由于走滑断裂破坏了山前洪积扇与其汇水盆地...

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

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 A_f=γA_c(A_f is the alluvial-fan area,A_c 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.