Abstract: Invisible faults often developed in Quaternary unconsolidated sediments including concealed faults and die-out faults, which lead to complexity and multi-solution for paleoearthquake research. In this paper, original-state directional samples related to invisible or die-out faults are collected from some typical paleoearthquake profiles and solidified in laboratory. Microstructures have been observed after grinding slides in three-dimension coordinate system. Some indicators of invisible faults have been found in micrscopic field. The mechanisms of die-out faults have also been studied. It is suggested that according to microstructural observation, to confirm or negate the existence of concealed faults or to trace the terminated levels of die-out faults, can help us determine the age and periods of paleoearthquake events more accurately combining with macroscopic observation and age dating.

Key words: Invisible fault, Microstructure, Quaternary unconsolidated sediments, Paleoearthquake

摘要： 第四纪松散沉积物中普遍存在断层的隐性现象,包括断层的隐形和尖灭,给古地震研究带来了复杂性和多解性。选择了一些典型古地震剖面,对涉及到断层隐形或尖灭的部位,进行了定向原状样品采集,通过室内样品固结,显微薄片制作和显微构造现象观察,从显微域里找到了鉴定隐形断层的许多标志,并对断层尖灭机制进行了研究。认为通过显微构造分析,排除或肯定隐形断层的存在,或者追踪断层尖灭的层位,结合宏观剖面研究和年代测定,可以使古地震时代和期次判定更准确。

关键词: 隐形断层, 显微构造, 第四纪松散沉积物, 古地震