Riedel shear structures in the co-seismic surface rupture zone produced by the 2001 M w 7.8 Kunlun earthquake, northern Tibetan Plateau
We present a case study of Riedel shear structures related to the co-seismic surface ruptures produced during the 2001 M w 7.8 Kunlun earthquake in northern Tibet, which are related to strike-slip movement along the Kunlun Fault. Field investigations and interpretations of high-resolution remote sen...
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Published in | Journal of structural geology Vol. 33; no. 9; pp. 1302 - 1311 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
Elsevier Ltd
01.09.2011
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Subjects | |
Online Access | Get full text |
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Summary: | We present a case study of Riedel shear structures related to the co-seismic surface ruptures produced during the 2001 M
w 7.8 Kunlun earthquake in northern Tibet, which are related to strike-slip movement along the Kunlun Fault. Field investigations and interpretations of high-resolution remote sensing images show that the 2001 co-seismic surface ruptures, striking WNW–ESE, are mainly characterized by Riedel shear structures, including
T fractures, and
R, Y, and
P shears. A left-lateral shear sense is indicated. To assess the Riedel shear fabrics quantitatively, we measured the azimuth of 19,455 co-seismic surface rupture strands, the width of rupture zones at 474 profiles, and 336 fold axes of mole track structures, using 1-m-resolution IKONOS and 0.61-m-resolution QuickBird images acquired soon after the earthquake. The analytical results show that i) the co-seismic surface ruptures are generally concentrated in up to five subparallel sub-rupture zones, with individual sub-rupture zones varying in width from 3 to 350 m (generally <100 m); ii) the total width across all sub-rupture zones is generally <500 m (though locally >1–2 km); iii)
T fractures are mainly developed within the alluvial deposits at counterclockwise angles of 15–40° relative to the general trend of the rupture zone; iv)
P shears are also mainly found in the alluvial deposits, but at counterclockwise to clockwise angles of 5–10° relative to the general trend; and v)
Y and
R shears are developed within both the alluvial deposits and basement rocks, mainly representing the reactivation of pre-existing fault traces. The results demonstrate that the co-seismic Riedel shear structures are primarily controlled by the local geology during surface rupture formation, consistent with the idea that Riedel shear structures are common fault patterns within strike-slip shear zones and that their development is related to the early stages of fault evolution.
► The surface ruptures produced by the 2001 M
w 7.8 Kunlun earthquake are mainly characterized by Riedel shear structures. ► The Riedel shear structures include
T fractures, and
R,
Y, and
P shears, which are concentrated in a zone of <500 m in width. ► The lower-angle synthetic
R,
P, and
Y shears are inclined at <15° and −10° to the fault trend, indicating a left-lateral shear sense. ► The higher-angle
T fractures are developed mainly within alluvial deposits, oriented at angles of 15–40° to the fault trend. ► The development of Riedel shear structures is related to the early stages of strike-slip fault evolution. |
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ISSN: | 0191-8141 1873-1201 |
DOI: | 10.1016/j.jsg.2011.07.003 |