走滑断裂叠置拉张区构造变形的物理模拟及启示

走滑断裂叠置拉张区构造变形的物理模拟及启示

任健;官大勇;陈兴鹏;刘朋波

【摘要】The calculation of strike-slip displacement is an important content in the study of strike-slip tectonics.Analogue modeling of releasing stepovers in strike-slip faults can be used to calculate the displacement.This paper utilizes the dual-layer model composed of brittle overburden and ductile layer.The model may represent a detachment level at crustal scale or a weak sedimentary layer at basin scale,and can simulate the stepovers like those in the natural situations.Two types of secondary faults can be observed in the stepovers part including the transverse faults striking at 80°-90° (T fractures) to the applied shear direction and the oblique faults striking at nearly 45° clockwise (R shears) with r espect to the shear direction.In the experiment,by altering the overlapping length and offset distance of two main faults and the applied strike-slip displacement,we can calculate the gradual change of the ratio between transverse faults and oblique faults and identify the relationship among the variables by means of data fitting.The results show that (1) the increase of overlapping length and strike-slip displacement or the decrease of offset distance will both result in higher ratio of transverse faults to oblique faults;(2) four measured variables in every experiment have specific logarithmic relationship and proportional reduced analogue modeling experiment compared to the extensional strike-slip stepovers in the natural world could be conducted to acquire the function relationship

among overlapping length,offset distance,ratio between two types of faults and strike-slip displacement so that the first three measured data can be used to calculate the strike-slip displacement conversely.The calculation of strike-slip displacement of the Tan-Lu fault zone in Liaodong Bay,Bohai sea by using analogue modelling method showed that the dextral strike-slip displacement from neotectonics is about 2.1 km,which could provide guidance for the hydrocarbon exploration in this area.%走滑断层的走滑量研究是构造分析过程中的关键,本文运用走滑断裂拉张叠置部位的构造物理模拟方法作为走滑量求取的手段,利用与自然界吻合程度较好的脆性-塑性双层模型对走滑拉张叠置部位进行模拟,发现叠置区主要发育与主边界断层呈80°～90°的横向断层(T断层)和呈顺时针45°的斜向断层(R剪切)两种类型的次级断层.通过改变实验中走滑断裂的叠置长度、横向间隔距离以及走滑量,计算不同实验中横向断层与斜向断层数量的比例并对实测数据进行拟合,结果显示:(1)叠置长度以及走滑量的增加或者横向间隔距离的减小,都会导致横向断层与斜向断层数量比的增加;(2)每组实验中的上述四个实测变量之间存在着特定的对数关系,通过对自然界中的走滑断裂拉张叠置区进行同比例缩小的构造物理模拟实验,获得四者之间的函数关系,从而可以确定走滑量.将构造物理模拟计算走滑量方法应用于渤海海域辽东湾地区郯庐断裂带,得到其新构造运动以来约发生了2.1 km的右旋走滑活动.

【期刊名称】《大地构造与成矿学》

【年(卷),期】2017(041)003

【总页数】11页(P455-465)

【关键词】走滑断层;叠置带;构造物理模拟;走滑量;郯庐断裂带

【作者】任健;官大勇;陈兴鹏;刘朋波

【作者单位】中海石油(中国)天津分公司渤海石油研究院,天津300459;中海石油(中国)天津分公司渤海石油研究院,天津300459;中国石油大学(华东)地球科学与技术学院,山东青岛266580;中海石油(中国)天津分公司渤海石油研究院,天津300459【正文语种】中文

【中图分类】P542

走滑构造作用是指在剪应力作用下板块发生水平运动而产生的构造作用, 是影响地球岩石圈地貌的一个基本的作用过程, 在区域地质构造研究中具有重要地位。目前, 国内外已有大量关于走滑构造作用的系统性研究成果(Wilcox et al., 1973; Sylvester, 1988; 刘和甫等, 2004; Mann, 2007; Dooley and Schreurs, 2012)。而构造物理模拟方法一直以来都是研究走滑构造几何学特征和演化机制的常规手段(Wilcox et al., 1973; Naylor et al., 1986; Dooley, 1994; An, 1998)。自20世纪80年代初, 走滑断裂叠置区(stepover)概念被明确提出以来(Mann et al., 1983; Bahat, 1984; Aydin and Nur, 1985), 关于走滑断裂拉张叠置位置(Dooley, 1994; Richard et al., 1995; Dooley and McClay, 1997; Rahe et al., 1998; Dooley et al., 1999; Sims et al., 1999; Basile and Brun, 1999; Atmaoui et al., 2006; Wu et al., 2009; Mitra and Paul, 2011)和挤压叠置位置(Richard et al., 1995; Keller et al., 1997; Dooley et al., 1999; McClay and Bonora, 2001; Mitra and Paul, 2011)发育特征的构造物理模拟研究也一并大量地进行, 尤其是因为走滑断裂拉张叠置部位常常是走滑拉分盆地发育的潜在位置之一,更是构造物理模拟的研究热点, 当中的大部分实验都运用模拟走滑断裂弯曲部位的刚性基底模型模拟走滑断裂叠置区, 虽然刚性基底模型与走滑断裂弯曲部位的实际情况有着较好的吻合性, 但是走