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| Titel |
Late Quaternary slip rates and paleoearthquakes along the Yabrai range-front fault in the southern Gobi-Alashan block |
| VerfasserIn |
Jingxing Yu, Wenjun Zheng, Qiyun Lei, Yanxiu Shao, Weipeng Ge |
| 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 |
250094947
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| Publikation (Nr.) |
 EGU/EGU2014-10381.pdf |
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| Zusammenfassung |
| Study on the active faults of the southern Gobi-Alashan block is significant to understand the
tectonic deformation processes associated with the Tibetan Plateau and Ordos block. With
this knowledge in mind, the present study aims to answer what the major process is governing
the tectonic deformation and the structural relationships between Gobi-Alashan and adjacent
regions. Since this area was featured by late Quaternary active tectonics, the activities and
paleoearthquakes around the block need be studied and reconciled. So, we will focus on one
of those active structures, the ranger-front fault along Yabrai Shan, to address some basic
problems.
Three aspects are analyzed, i.e., geomorphology, kinematic characteristics and
paleoearthquakes of the range-front fault along the Yabrai Shan. By combining
previous studies and Differential GPS measurements, implications of the fault for the
regional tectonics has been discussed. The main conclusions are summarized as
follows:
This fault consists of three segments. The most active segment is in the southwest. The
southwest segment is about 35 km long. Its scarp, about 1-2 m high, might be the result of the
most recent event (MRE) and stretches NE60° almost the full segment. Existence of free
surface indicates that the elapsed time of the last event must be not long. The middle segment
is about 31 km in length. Just a single fault plane was identified along the main bounds of
the Yabrai Shan, but the fault consists of several splays in the north. In contrast
to the simple geometric structure of the middle segment, the northeast segment
comprises several faults. Scarps of the most recent earthquake event are clear but
tend not to be continued. Field investigation reveals about 0.5-1.5 m up to 2 m
height.
This work determined slip rates by combining fault-scarp measurements and cosmogenic
exposure age dating. Study on slip rates shows that the Holocene dip-slip rate of the Yabrai
fault is 0.11±0.03 mm/a. Scarp vertical heights along the fault show that the middle
and north segments have obviously higher displacements than the southwestern
segment.
Trenching and field survey along the surface ruptures indicate that there were five strong
earthquakes along the range-front fault. The most recent event on the fault was
about 1.5 ka ago, and the others were dated the late Pleistocene, i.e., >60 ka, >50
ka, ~30 ka, ~ 3 ka, respectively, with about 10 ka recurrence interval of major
earthquakes.
A previous seismic reflection profile suggests that the Yabrai Shan range-front fault was
evolved as a normal fault since Cretaceous before the presence and formation of the Tibetan
Plateau. Therefore, this work concluded that the range-front fault of the Yabrai Shan is not
resulted from the Indo-Asian collision. It should be studied whether the outward growth of
the Tibetan Plateau governs tectonic deformation of the fault today, and which deformation
model is suitable for the regions adjacent to Tibet, Ordos and Gobi-Alashan. This study
would play a great role for constraining the tectonic evolution of the Tibetan Plateau. |
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