负反转断裂主反转期和反转强度分析

以塔里木盆地北部隆起轮台断裂带为例，提出了非坪一坡式结构、具有多期道冲作用的负反转断裂演化模式。负反转断裂的发展演化可分为初始沉积阶段、早期冲断剥蚀阶段、同生冲断阶段和负反转阶段。早期的同生逆断层序和后期的负反转层序是识别负反转断裂的关键标志。位移一距离曲线上的“拐点”代表了断层由冲断活动向负反转活动转化的转折点，指示了主反转期。而“零点”则代表了断层上从净收缩转化为净引张的转折点。根据“零点”在同生逆断层序中的位置变化，可以确定断层的反转率或反转强度。同时，断层生长指数也反映了负反转强度的大小。对塔里木盆地北部隆起轮台断裂带进行的实例分析表明，轮台负反转断裂主反转期为中新世苏维依期一吉迪克期，反转率为０．８５～０．９８。

ANALYSIS ON MAIN INVERSION PHASE AND INTENSITY OF NEGA-TIVE INVERSION FAULT

A model for the negative inversion fault with non-flat-ramp geometry is proposed. Negative inversion fault involves the reversal of contractional fault which turns into normal dip-slip displacement along the existing thrust fault plane during extensional movement. The development of a negative inversion fault may be devided into (1) primary sedimentation stage, (2)early thrust and erosion stage,(3)contemporaneous thrusting stage, and(4) negative inversion stage. The key marks to recognize a negative inversion fault are the contemporaneous thrust sequcnces and negative inversion sequences. The point of change from thrusting to negative inversion faulting in the displacement-distance plot is the inflection point which represents the main inversion phase. And the point of transformation from net constraction to net extension is the null point. The inversion ratio or intensity can be determined by the position of null point in contemporaneous thrust sequences. The negative inversion intensity can also be given by fault growth index. Taking Luntai fault belt of northern Tarim uplift as an example, the main negative inversion phase of the fault may be Suwiyi-Jidike epoch of Miocene, and the inversion ratio is 0.85~0.98.