Abstract:The most intense neotectonic activities in Sichuan province occurred at least three times in the history. The first episode occurred during the time between Eogene and Neogene, the second between Neogene and early Pleistocene and, the third between early Pleistocene and middle Pleistocene. They control the activities of various types of structural zones and structural systems respectively, and through complex evolutions they finally take complicated forms of structural contours and mountains and rivers. The structural patterns formed in Neiod are as follows:east-west structural zone, north-south structural zone, chess-board structures, Neocahaysian system, Qinghai-Xizang system, rotational shear structures and so on. The structural stress fields and their trasitional models reflected by the generations and evolutions of all the structural zones and their genetic sequences occurred with good regularity. As a whole, the north-south trending compression was earlier than the east-west trending compression. Active structures occur within Sichuan province from middle pleistocene up to present with north-south trending compression fractures and the related large-seale chess-board structures composed of north-east and northwest trending fractures as the main part and, with folded fractures in western Sichuan province of Neocathaysian system and Qinghai-Xizang system as the secondary part, it is of instructive significance to select the active structures to the study of seismogeology and engineering geology.
