基于断层滑动数据古应力反演的影响因素及其误差分析

古构造应力场是构造动力学研究中的一个重要内容，且断层滑动数据古应力反演已经成为古构造应力场恢复研究中比较常用的重要方法之一。近年来，断层滑动数据古应力反演方法研究和应用取得了一系列重要进展，但有关反演结果的解释仍存歧义，反演结果的影响因素及其误差范围等并未得到深入研究与定量分析。本文总结指出，影响断层滑动数据古应力反演结果的主要因素包括变形体制、剪切破裂面类型、断层面的形态以及地质体内薄弱面的存在等。在此基础上，分别对新生断层和先存薄弱面滑动数据的古应力反演综合误差进行了定量分析。研究指出，在可以大致厘定变形体制或误差在允许范围内的前提下，将断层滑动数据反演结果解释为应力状态是合理可行的。各种因素导致的反演误差定量分析表明，同一期构造应力场形成的破裂面滑动数据的古应力方位反演误差最大不超过35°。换言之，在没有证据表明存在不同期次的应力作用情况下，主应力方位变化小于35° 的应力状态，可以划归同一期应力场。

Factors affecting the paleostress inversion from fault-slip data and error analysis

Paleostress field is one of the key aspects in the geodynamic analysis, and paleostress inversion of fault-slip data has been becoming an important approach in the reconstruction of paleostress field and improved greatly as well as employed widely in last two decades. There are, however, still many problems remain controversial, such as, strain or stress interpretation of the inversion results, impact factors controlling the inversion results and their errors. In this paper, the main factors affecting the result of paleostress inversion of fault-slip data are summarized as pure shear or simple shear strain regime, shear fracture type among Riedel shear system, length-to-width ratio of fracture and weak fabric or pre-existing fractures within geologic terrane as well. Comprehensive errors of paleostress inversion both from primary fractures and pre-existing weakness planes have been quantitatively analyzed in detail. It is proposed that the inversion results could be interpreted as stress states if the pure shear or simple shear regime can be clarified or the deviation is within the limit of error. Quantitative analysis in this paper implies that the inversion errors of principle stress direction should be confined less than 35° if the data were collected from faults formed under a specific tectonic stress filed. In other word, the inversion results with a direction deviation less than 35° could be grouped into one generation of paleostress field, if there is no evidence indicating that they were derived from different tectonic deformations.