Spatial variability of modern tectonic stress fields in the north‐eastern margin of Tibetan Plateau

Abstract

A modern tectonic stress field for the northeastern margin of Tibetan Plateau was determined using linear inversion. Focal mechanism solutions and the depths of 54 earthquakes from 2009 to 2017 were obtained from broadband seismic waveforms. We derived the tectonic stress field using the SATSI (Spatial and Temporal Stress Inversion) software based on the damped linear inversion method. The stress tensor structures are primarily indicative of strike-slip and thrust faulting; their distributions are controlled by the West Qinling and Haiyuan faults. The Longxi Block is surrounded by two faults dominated by thrust faulting; the regions in the periphery of the faults, (e.g., West Qingling Fault Zone and Liupanshan Basin) are primarily characterized by strike-slip faulting. However, normal faulting has developed in the Haiyuan-Zhongwei Belt of Liupanshan Basin, indicating that the latest tectonic regime is an NNW-SSE extension instead of a strike-slip fault with a thrust component, as has been previously suggested. This anomalous stress mechanism reflects the combined effects of block rotation and local extension resulting from movement along strike-slip faults. The West Qinling Fault is dominated by thrust faulting instead of strike-slip faulting. The Haiyuan-Liupanshan and Niushoushan-Luoshan faults are predominantly strike-slip faulting. The directions of the maximum stress axes (σ1) in both Liupanshan Basin and the Longxi Block are ENE-WSW down to Liupanshan in the south and West Qinling Fault Zone, where the stress axes gradually rotate clockwise to E-W. The modern tectonic stress field implies that regional stress originates from far-field effects of Indian and Eurasian plate collision. K E Y W O R D S focal mechanism solutions, Liupanshan Basin, northeastern margin of Tibetan Plateau, tectonic stress field, West Qinling Fault Zone 1 | INTRODUCTION The leading edge of growth and expansion of the Tibetan Plateau is along the northeastern margin, which is a modern geomorphologic and tectonic feature formed by ordered extension of the plateau during its gradual formation (

Numerical simulation of contemporary kinematics at the northeastern Tibetan Plateau and its implications for seismic hazard assessment

“…The dominant depth range of seismic activities in the study area is 5-15 km, with a few events at depths up to 20 km (L. Li et al, 2020;. As mentioned in the introduction, seismic activities are closely related to fault activities.…”

Numerical Simulation of Present-day Kinematics at the Northeastern Margin of the Tibetan Plateau

“…The dominant depth range of seismic activities in the study area is 5-15 km, with a few events at depths up to 20 km (Li et al, 2020). Therefore, we extracted the kinematic characteristics up to a depth of 20 km for the main faults of the study area using our 3D geomechanics model.…”

“…It has been estimated that 1400 years have elapsed since its last activation (Xue, 2014). 360 (Gan et al, 2002); L1 is the length of the fault (Xu et al, 2016); L2 is the width of the fault, measured at the dominant focal depth of the region (Li et al, 2020); μ is the shear modulus of the rocks (Aki et al, 2002); t is the time that has elapsed since the most recent earthquake (Gan et al, 2002;Shi et al, 2013Shi et al, , 2014Wang et al, 2001); S is the largest maximum coseismic slip, calculated using the method of Gan et al (2002); Ms is the earthquake magnitude corresponding to the energy accumulated by the fault between recurrences (Purcaru et al, 1978); T is the recurrence interval of the fault, where T = S/(V1-V2) (Shen et al, 2009). The fault names are defined in Figure 1 and Figure 14.…”

Active tectonics and palaeo‐environmental change in West China ‐ Preface

“…Li , Rao, Qiu, He and Gao (2020) integrated the observed focal mechanism solutions since 1976, the velocity vectors of 25 years of GPS measurements, and the results of existing field studies on active structures in the eastern Tian Shan, to demonstrate that slip partitioning under oblique convergence is the main characteristic of active deformation. Meanwhile, they suggested that constraints on intermontane structures are still needed in future investigations for better constraining the strain distribution in the eastern Tian Shan.…”