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Paleoseismic Characteristics of Dachaidan Fault in Qinghai(PDF)


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Paleoseismic Characteristics of Dachaidan Fault in Qinghai
PANG Wei HE Wen-gui YUAN Dao-yang ZHANG Bo WU Zhao
1. Lanzhou Institute of Seismology, China Earthquake Administration, Lanzhou 730000, Gansu, China; 2. Lanzhou Scientific and Technical Innovation Base, Institute of Earthquake Science, China Earthquake Administration, Lanzhou 730000, Gansu, China
paleoseismic Dachaidan fault scarp trench 14C dating recurrence interval Qaidam Basin
By means of satellite image interpretation, a distinct continuous active fault zone, which is called Dachaidan fault, has been found on the diluvial fan in the east piedmont of Dachaidan of Haixi area, Qinghai. Field investigation confirms that the fault is a NNW-direction active fault (about 340°) with a length of about 125 km. This fault is an important part of fault system in the northern margin of Qaidam Basin; the fault in Late Quaternary shows extrusion and thrust with dextral strike-slip component tectonically. There are faulted landforms including multi-level small fault scarps, fault ditch and dextral gully preserved in the piedmont alluvial-diluvial fan. Differential GPS surveying results show that the height of a single small scarp is 0.5-1 m, and generally up to 3-5 m for a plurality of scarps. According to the comprehensive analysis of 2 natural paleoseismic profiles and 3 trench profiles, the main fault in the front is thrust fault with the performance of a group of tensional normal faults in the back. The latest tectonic activity suggests that the fault has gradually extended to the piedmont. 14C dating results indicate that 5 paleoseismic events are confirmed on Dachaidan fault, particularly 4 events since Holocene; occurrence time of paleoseismic events has the characteristics of quasi periodicity at the recurrence interval of about 2 000 years. The elapsed time for the recent paleoseismic event is (1 935+60) a B.P., which indicates that the elapsed time and recurrence interval of Dachaidan fault are close, resulting in high earthquake risk.




Last Update: 2015-05-27