Evolution of the late Cenozoic tectonic stress regime in the Shanxi Rift, central North China Plate inferred from new fault kinematic analysis

29 oriented and 10 nonoriented coal samples are collected in the study from three different regions of the Huaibei coalfield, eastern China, and their vitrinite reflectance indicating surface (RIS) parameters are systematically calculated and analyzed. Using the available methods, Kilby’s transformations and RIS triaxial orientations are obtained. The magnitudes and orientations of the RIS axes of the three regions were respectively projected on the horizontal planes and vertical sections. The results show that the samples in high deformed region have significant anisotropy magnitudes (higher Bw/Rmax and Ram values) with a biaxial negative style, whereas the samples in the slightly deformed area have unimpressive anisotropy magnitudes with a biaxial negative style. Thermal metamorphism superposed might enhance the complication and variation of RIS style. RIS projection analysis deduced that the RIS orientation is mainly controlled by regional tectonic stress, and likely influenced by deformation mechanisms of coal.

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Tectonic stress regime in the 2003–2004 and 2012–2015 earthquake swarms in the Ubaye Valley, French Alps

Pure and Applied Geophysics ◽

10.1007/s00024-018-1792-2 ◽

2018 ◽

Vol 175 (6) ◽

pp. 1997-2008 ◽

Cited By ~ 6

Author(s):

Lucia Fojtíková ◽

Václav Vavryčuk

Keyword(s):

Seismic Activity ◽

Joint Inversion ◽

Earthquake Swarm ◽

Active Faults ◽

Tectonic Stress ◽

Geological Mapping ◽

Earthquake Swarms ◽

Stress Regime ◽

French Alps ◽

Principal Axes

Abstract We study two earthquake swarms that occurred in the Ubaye Valley, French Alps within the past decade: the 2003–2004 earthquake swarm with the strongest shock of magnitude ML = 2.7, and the 2012–2015 earthquake swarm with the strongest shock of magnitude ML = 4.8. The 2003–2004 seismic activity clustered along a 9-km-long rupture zone at depth between 3 and 8 km. The 2012–2015 activity occurred a few kilometres to the northwest from the previous one. We applied the iterative joint inversion for stress and fault orientations developed by Vavryčuk (2014) to focal mechanisms of 74 events of the 2003–2004 swarm and of 13 strongest events of the 2012–2015 swarm. The retrieved stress regime is consistent for both seismic activities. The σ 3 principal axis is nearly horizontal with azimuth of ~ 103°. The σ 1 and σ 2 principal axes are inclined and their stress magnitudes are similar. The active faults are optimally oriented for shear faulting with respect to tectonic stress and differ from major fault systems known from geological mapping in the region. The estimated low value of friction coefficient at the faults 0.2–0.3 supports an idea of seismic activity triggered or strongly affected by presence of fluids.

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The petrochemistry of the Lower Proterozoic metamorphic rocks from the Dabieshan-Lianyungang area, the southeastern margin of the North China Platform

Mineralogical Magazine ◽

10.1180/minmag.1991.055.379.15 ◽

1991 ◽

Vol 55 (379) ◽

pp. 263-276 ◽

Cited By ~ 3

Author(s):

Sang Longkang

Keyword(s):

Continental Margin ◽

North China ◽

Active Continental Margin ◽

The South ◽

North China Platform ◽

The North ◽

Lower Proterozoic ◽

Southeastern Margin ◽

Tectonic Settings ◽

North China Plate

AbstractBased on geological studies, 141 rock analyses and 5 trace element analyses of metabasites, the present paper deals with the rock association, chemical features, protolith formation and the original tectonic settings upwards through the Lower Proterozoic metamorphic strata in the Dabieshan-Lianyungang area, in the south-east of the North China Platform. The results of the study indicate that the lower and middle parts of the metamorphic strata comprise terrigenous clastics, phosphoritic and aluminous sedimentary formations which formed under stable continental margin conditions. In the middle-upper part a calc-alkaline volcano-sedimentary formation under the active continental margin was developed. The Lower Proterozoic meta-strata of sedimentary-volcanosedimentary origin from bottom upwards suggest that the tectonic evolution of the south-eastern margin of the North China Platform is a process from stabilization to mobilization. This process suggests a northward subduction of the Yangtze Plate under the North China Plate during the later part of the early Proterozoic.

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