Tan-Lu Fault Zone in Offshore Bohai Bay Basin, Eastern China: New Structural Observations From High-Quality 3-D Seismic Data

Abstract

The NE-trending Tan-Lu fault zone is a large-scale strike-slipping fault zone which traverses the eastern side of the Bohai Bay basin, eastern China. There are many controversies on its deformation and evolution for a long time. In order to meet the needs of oil and gas exploration in the offshore Bohai Bay basin, many high-quality 3D seismic surverys have been acquired in the past decade, which affords an exceptional opportunity to study the structural features of the Tan-Lu fault zone. The newest 3D seismic data show that the along-strike segmentation of the Tan-Lu fault zone are obvious in the offshore Bohai Bay basin. Based on its deformation difference in various areas, the Tan-Lu fault zone can be divided into three large segments with more subsegments. The northern segment which is located in the eastern part of the Liaodongwan depression has the narrowest distribution area in plane, and the most predominant strike-slipping characteristics. The segment comprise of 2–3 major faults with length of about 200km, which act as the boundary faults between elongated uplifts and sags. The middle segment in the Bozhong depression is composed of several branch fault zones with poor continuity and wider distribution area. The part has mixed features of strike-slipping and extensional deformation. The southern segment in the Bonan depression which is mainly controlled by EW-trending extensional faults comprises of three branch fault zones, each of them has multiple faults. The segment has the widest distribution area, and the branch fault zones are nearly vertical in cross sections. Compared to EW-trending extensional faults, the NNE-trending southern segment experienced later activity and cut the former extensional faults. The former studies addressed that the rhombic sags within the Bonan depression were pull-apart subbasin resulted from the dextral strike-slipping movement of the Tan-Lu fault zone. The new 3D seismic data, however, confirm that they should be extensional faulted sags which are also reformed by the Tau-Lu fault zone.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015