Discussion on the Compression-Shear Activity of the Tazang Fault
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Institute of earthquake Science,Institute of earthquake Science, CEA,Institute of earthquake Science, CEA,Institute of earthquake Science, CEA,China seismological bureau first monitoring center,Seismological bureau of Shandong province

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    Abstract:

    Tazang fault in the eastern section of East Kunlun fault traverses the interior and boundary of the eastern margin of the Qinghai-Tibet plateau. As the northeastern boundary of the southeastward movement of Bayankala terrane, its active features and sliding rate in Late Quaternary are extremely important to understanding the tectonic deformation of the Qinghai-Tibet plateau. Combined with interpretation of the high-resolution remote sensing images obtained through SPOT and ASTER DEM, this study carried out detail research on offset strata and landform and geochronology using seismic data and morphological features (such as streams, mountain ridges, displaced fluvial fans, terrace, fault valley, reversed camp, and so on), so as to understand the distribution, activity and strikeslip rate of the Tazang faults in late Quaternary. The Tazang fault can be divided into from west to east: Luocha section in the Qinghai-Tibet plateau, Dongbeicun section and Majiamo section in the margin of the Qinghai-Tibet plateau, with each section trending to 113°, 142° and 130° respectively, and gradually turning toward south. Its activity in late Quaternary is characterized by multiple stages and episodes. The Luocha section was dominated by sinistral shear strikeslip in company with compression during Holocene, with a sinistral strike-slip rate of 2.43~2.89 mm/a. Since 0.66±0.04ka BP when the latest offsetting event occurred, the fault surface is characteristic of nearly vertical strike slipping and welldeveloped tensional filled fractures. The Tazang fault is one of the major faults in the eastern extension of the East Kunlun fault system. The Majiamo section may be the active fault in Holocene, and 9.0±0.8ka stratum was faulted, with the fault surface dipping north up to 58°. Therefore, comparative analysis of activities of each segment in the Tazang fault shows that the western section was predominantly horizontal shear movement, the eastern section had a decreasing strikeslip motion component, and north-dipping of fault surface and uprising of northern hanging wall both resulted in gradually increasing of the vertical component. Strike-slip of East Kunlun fault zone and Tazang fault tended to decrease eastward in late Quaternary, and was converted into horizontal thrusting and plateau uplift, which is consistent with the features of the “imbricated thrust conversion-limited extrusion” model.

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HU Chaozhong, REN Jinwei, YANG Panxin, XIONG Renwei, CHEN Changyun, FU Jundong.2017. Discussion on the Compression-Shear Activity of the Tazang Fault[J]. Acta Geologica Sinica,91(7):1401-1415

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History
  • Received:September 05,2016
  • Revised:December 23,2016
  • Adopted:December 24,2016
  • Online: July 11,2017
  • Published: