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Crustal structure of the northern margin of the eastern Tien Shan, China, and its tectonic implications for the 1906 M???7.7 Manas earthquake

Earth and Planetary Science Letters

By:
, , ,
DOI: 10.1016/j.epsl.2004.04.015

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Abstract

The Tien Shan orogenic belt is the most active intracontinental mountain belt in the world. We describe an 86-km-long N-S-trending deep seismic reflection profile (which passes through the southern Junggar basin) located on the northeastern Tien Shan piedmont. Two distinct anticlines beneath the northern margin of the Tien Shan are clearly imaged in the seismic section. In addition, we have imaged two detachment surfaces at depths of ???7 and ???16 km. The detachment surface at 16-km depth corresponds to the main detachment that converges with the steep angle reverse fault (the Junggar Southern Marginal Fault) on which the 1906 M???7.7 Manas earthquake occurred. A 12-14-km-thick sedimentary basin is imaged beneath the southern Junggar basin near Shihezi. The crust beneath the northern margin of the Tien Shan is 50-55-km thick, and decreases beneath the Junggar basin to 40-45-km thick. The crustal image of the deep seismic reflection profile is consistent with models derived from nearby seismic refraction data and Bouguer gravity anomalies in the same region. The faulting associated with the 1906 Manas earthquake also fits within the structural framework imaged by the seismic reflection profile. Present-day micro-seismicity shows a hypocentral depth-distribution between 5 and 35 km, with a peak at 20 km. We hypothesize that the 1906 Manas earthquake initiated at a depth of ???20 km and propagated upwards, causing northward slip on the sub-horizontal detachments beneath the southern Junggar basin. Thus, in accord with regional geological mapping, the current shortening within the eastern Tien Shan is accommodated both by high-angle reverse faulting and detachment faulting that can be clearly imaged at depth in seismic reflection data. ?? 2004 Published by Elsevier B.V.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Crustal structure of the northern margin of the eastern Tien Shan, China, and its tectonic implications for the 1906 M???7.7 Manas earthquake
Series title:
Earth and Planetary Science Letters
DOI:
10.1016/j.epsl.2004.04.015
Volume
223
Issue:
1-2
Year Published:
2004
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
187
Last page:
202
Number of Pages:
16