| Wenchuan Earthquake Fault Zone Scientific Drilling (WFSD) was co-organizedby Ministry of Science and Technology， Ministry of Land and Resources and ChinaBureau of Earthquake. The WFSD project plans to drill5scientific wells on thehanging wall of co-seismic surface rupture zones, including the Yingxiu-Beichuanfault zone and Anxian-Guanxian fault zone, Longmen Shan. The WFSD-3P andWFSD-3drilling holes are located on the hanging wall of the Anxian-Guanxian Faultzone at Jiulong, Mianzhu, Sichuan province, the final depth are551.54m and1250.18m. Fundamental studies were taken for the WFSD-3drilling cores, such aspetrology, structural geology and filed cataloging. The results show that the cores candivided into three segments, including the fourth member of the Xujiahe Formation(0~264m), the third member of the Xujiahe Formation (264~1250m) and the fourthmember of the Xujiahe Formation (1250~1502m), from top to bottom, respectively.The Xujiahe Formation is Triassic sedimentation rocks with sandstone, slitstone,peliticsiltstone, conglomerate and coal beds (lines). The WFSD-3cores contain manyfault-rocks, such as fault breccia, cataclastic rock and fault gouge, the pseudotachyliteis not appeared in this well, which reflecting the brittle deformation. Age olderformation pressure in the time a new formation on, show that Anxian-Guanxian faultzone is not a single section, but by many of the fault of the complex of fault zone, andthrust lithologic sheets object into it. Twenty-six fault zones are detected in this well,including the three main major fault zone FZ634, FZ1215and FZ1250, and theFZ1250is the possible primary slip zone during the2008Wenchuan earthquake. Thedip angles are variable among~60°,~46°and~38°for the trench, WFSD-3P andWFSD-3, respectively. The variation of the dip indicates that the Anxian-Guanxianfault is a listric thrust fault with low dip angle. |
PDF Full Text Request