琼东南盆地东部层间断层系及其形成机制分析

基于琼东南盆地最新3D地震资料的地质与地球物理解释,运用先进的地震剖面相干处理技术,在琼东南盆地东部早-中中新世泥岩中发现了大量层间断层,这些断层剖面上为板状正断层,倾角一般大于45°,长度不超过1000m,但是平面走向在不同区域差异很大。研究区层间断层为以体积收缩机制为主要形成机制,在区域应力、重力滑塌和超压水力破裂多种力学机制共同影响下形成的,基本限制在层间的、多种类型和多种性质的断层组合。研究区东北部主要为体积收缩机制形成的层间断层,并受到重力滑塌的影响,断层主要表现为平行于等深线的EW向的断层密集带和与之垂直的SN向直线状断层;中部主要受超压水力破裂作用和体积收缩机制的影响,断层主要由放射状断层和与之垂直的层间断层两部分组成;西南部地区主要受体积收缩作用和区域应力场的影响,在构造断层影响区,层间断层走向与构造断层相互垂直,未影响区则表现为断层多边形。

Geometrical Characteristics and Formation Mechanism of Intrastratal Faults in the Southeast of the Qiongdongnan Basin

Based on geological interpretation of the latest 3D seismic data,combined with drilling data,a large number of intrastratal faults have recently been identified in the early-middle Miocene mudstone from the southeast of the Qiongdongnan Basin(QDNB),using advanced coherence technology.Those faults are platy in seismic profile,more than 45° dipping,less than 1000m long,with diverse fault striking in different regions.Intrastratal faults,which are limited in layers,are variety of type composite faults formed by volumetric contraction under the influence of various mechanical mechanisms such as regional stress field,gravitational spreading and hydraulic fracture.In the northeast part of the studying area,the faults are composed of EW-trending densely faulted belt and SN-trending linear faults,which resulted from volumetric contraction and gravitational spreading.In the central part of the studying area,the faults are composed of radial faults and other faults perpendicular to the former,which formed by hydraulic fracture and volumetric contraction.In the southwest part of the studying area,the intrastratal faults were formed by volumetric contraction and regional stress,and the intrastratal faults are perpendicular to the tectonic faults in the tectonic faults-affected area,and exhibit polygonal faults in the non-tectonic faults-affected area.