Fault Characteristics Of The Oaidam Basin In Early Cenozoic From Seismic Attributes Analysis

Geological studies have indicated that the NS compressive stress had been soon passed to the north of the Tibetan Plateau after the collision of the India and Eurasia. Qaidam Basin locates in the northeast of Tibetan Plateau, through studying the deformation and stress characteristics of the Qaidam Basin in the early of Cenozoic, it will help to understand the early deformation mechanism and plateau structure in the Tibetan Plateau. This has important implications. There are covering thick sediments from Mesozoic to Cenozoic in the Qaidam Basin, which brings great difficulties to the fault research. In this thesis, I make full use of three-dimensional seismic data in the basin, and select the appropriate seismic attributes to carry out the faults studying work. By analyzing the spatial distribution characteristics of early faults, conforming the faults activity time, classifying the different faults systems, I discuss the activities of the Qaidam Basin in early Cenozoic, in the end, exploring the evolution characteristics of the Tibetan Plateau.This thesis is base on3D seismic data, after studying the tectonic activities of the Qaidam Basin in the early Cenozoic, the main research contents and the conclusions are summarized as follows:(1) Choosing and comparison the characters of multi-seismic attributes, mastering the algorithms of different attributes, understanding the property parameters settings, identifying the performance characteristics of faults in different seismic attributes, contrasting the results of each attribute calculation detailed, I choose coherence attribute, fault enhancement and ridge enhancement attributes, instantaneous attribute, spectrum decomposition attribute as the optimal methods. By multi-attribute analysis, I recognize that different faults systems are widely developed in the Qaidam Basin, and clarify the locations and relationships of the different faults systems.(2) Analysis of faults structural features, identifying the EW trend faults of the Qaidam Basin were development in early Cenozoic. Base of determining the styles of the early faults, ascertaining the tectonic movement and deformation characteristics of the Qaidam Basin in early Cenozoic. I conclude the EW trend thick-skinned thrust faults structures are the results of compressive stress in the whole basin. The early faults are en echelon distribution in the plane. The two EW and SN strike faults were formed of the same period in the southwest area of Qaidam Basin. The SN trending faults were due to the EW trending faults caused by lateral strike-slip extrusion. The faults in front of the Altun were formed with related to the activity of the Altyn Fault. All of the EW strike faults started to be active at ca.36Ma.(3) The characteristics of stress direction reflected the compressional tectonic deformation with sinistra movement in the Qaidam Basin(ca.36Ma). That proved the remote effects of the collision between the India and Eurasia arrived Qaidam Basin in ca.36Ma and the stress field has dispersive sinistral shear in the northern plateau margin.