1. China Aero Geophysical Survey and Remote Sensing Center for Natural Resources,Beijing 100083,China 2. School of Earth Science,Zhejiang University,Hangzhou 310012,China 3. Research Center of Structures in Oil and Gas Bearing Basins,Ministry of Education,Hangzhou 310012,China
Based on 2D and 3D seismic data, this study analyzes the geometric characteristics,horizontal shortening,and active time of the Alar fault in the southwestern Qaidam Basin in detail and explores the kinematic characteristics,formation mechanisms,and significance for hydrocarbon accumulation during the whole Cenozoic.The results are as follows.The Alar fault can be divided into the western segment in NWW trending and the eastern segment in nearly NS trending,which are nearly vertical. As shown in sections,the western segment inclines southward with a relatively small dip angle,while the eastern segment inclines westward with an almost vertical section.The Alar fault has been active since the Early Cenozoic.The activities of the western segment are dominated by thrust,with horizontal shortening and vertical uplift both exceeding 3 km and strike-slip motion for about 1 km.The activities in the eastern segment are dominated by dextral strike-slip motion,with horizontal shortening and vertical uplift of about 1 km and strike-slip motion of up to 3 km.The formation and activities of the Alar fault are jointly affected by the northward compression imposed by the Qimantage orogenic belt to the south and the Altun left-literal strike-slip fault to the west.There is a close spatial-temporal matching relationship between the fault activities and the formation of oil and gas in the southwestern Qaidam Basin.Therefore,the fault activities are of great significance for the formation of oil reservoirs.
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