模型正演与川中二叠系中小断层精细地质解释

SEISMIC MODELING AND INTERPRETATION FOR MINOR FAULTS OF PERMIAN IN THE CENTRAL PART OF SICHUAN BASIN

成都地质学院,成都610059

Chengdu College of Geology, Chengdu 610059

模型正演是地震解释的一项重要工具.针对川中二叠系中小断层及断层系统存在的地震反射异常现象及其多解性,本文通过合成地震记录进行地质层位与野外地震记录的精确对比与标定.使用二维模型正演方法重建断层系统的地震响应过程,由此剖析断层构造产生地震反射异常的形成机制.重点阐述了断檐的地震响应,包括断点的相位转换、低速层增厚引起的时间迟后效应及由此产生的假断点、断檐屏蔽杂乱反射区以及断棱楔形体的地震响应.揭示了地震反射异常体解释中的一些陷井及有助于断层精细解释的特殊标志,论述了各种不同落差、不同产状小断层的断点、断面解释问题.

This paper deal with two problems: the discrimination of minor fault structures from seismic abnormities and the feature interpretation for faults including the identification of breaking points and fault planes. Synthetic modeling was used for correlating geologic horizons with seismic records and reconstructing seismic responses for minor overthrust structures. Three facts arc indicative in identifying seismic abnormities, namely: 1) the phase conversion of seismic events at breaking points, 2) the time delay caused by low velocity beds, which may mislead to the interpretation as a fault and 3) the seismic events in disorder as a result of shadow zones and the seismic responses of cone-like protrusive structures. In addition, some measures for improving the fault interpretation are involved as well.