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| Titel |
Normal faulting in the northern Shanxi Grabens, China |
| VerfasserIn |
Tim Middleton, Richard Walker, Barry Parsons, Weitao Wang, Jean-Luc Schwenninger, Sarah Sherlock |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095810
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| Publikation (Nr.) |
 EGU/EGU2014-11284.pdf |
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| Zusammenfassung |
| The Ordos Plateau forms a piece of non-deforming continental lithosphere in northeastern
China. Despite being thousands of kilometres from the nearest plate boundary, numerous
devastating earthquakes have been recorded around the margins of the plateau over the past
2000 years. Continental deformation in this part of Asia is believed to be caused by the
ongoing collision of India with Eurasia; India is currently moving northwards at 40mm/a.
The rate of deformation around the Ordos Plateau, however, is significantly less; typical slip
rates for faults bordering the plateau are of the order of 1mm/a. This deformation is
nonetheless important because the adjacent North China Plain is one of the most
densely populated regions on Earth. The combined population of Beijing, Hebei
and Shanxi Provinces is in excess of 125 million people—all potentially at risk
from future earthquakes. Assessing the seismic hazard is clearly of vital societal
importance.
The plateau is surrounded by extensional rift systems on all sides, except for the
Liupanshan in the southwestern corner, where thrust faulting is dominant. The Hetao Graben
lies to the north of the plateau, the Yinchuan Graben to the west, the Weihe Graben to the
south and the Shanxi Grabens to the east, where they form an S-shaped series of en-echelon
basins some 1200km long. The northern portion of the Shanxi Grabens is characterised by
east-northeast striking normal faults and asymmetric half-grabens with footwall blocks tilted
to the south-southeast. GPS measurements in this region are sparse, but the existing data
suggests a rate of extension across the northern Shanxi grabens of anywhere between 0mm/a
and 4mm/a.
We have used optically stimulated luminescence dating of sedimentary quartz grains and
Ar-Ar dating of basaltic lavas to determine ages for features which have been offset by the
faulting. Combined with scarp heights and field measurements of fault dip, this data suggest a
total extension rate across the northern Shanxi grabens that may be up to 3.6-6.5 mm/a.
Qualitative observations of the tectonic geomorphology also provide evidence for fault
growth and segment linkage in the region. Further work is needed to corroborate these slip
rates, but the comparatively high rates obtained in this study may have implications for future
seismic hazard. |
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