Abstract: Shallow seismic reflection method is a commonly used technique in urban active fault detection,however,special geotectonic environment may sometimes make reflection survey inapplicable.In such cases,high-resolution seismic refraction could be a feasible option.In this study,we use the finite difference method as the main technique and the conventional methods of refraction data interpretation as auxiliary means in the interpretation of high-resolution shallow refraction data for active fault detection in Lanzhou area.After a comprehensive analysis of first-break refraction travel-time characteristics,the velocity structure and interface structure along each profile have been obtained.A detailed description of the detection results from SS04-1 and SS11-2 seismic profiles is presented in this paper.The main stratigraphic interfaces and tectonic features identified by the two profiles are quite consistent with the results from drilling surveys along the profiles.Our results indicate that high-resolution seismic refraction is an effective replacement in areas where reflection seismic survey is hard to carry out.

Key words: urban active fault detection, high-resolution seismic refraction, Lanzhou City

摘要： 浅层反射波法地震勘探是城市活断层探测通常采用的方法,然而特殊的地质构造条件常会使反射波法勘探失效,此时可尝试利用高分辨折射波地震勘探方法。在兰州市活断层浅层高分辨折射地震资料的解释中,笔者以初至时有限差分层析成像方法为主,结合常规折射波资料解释方法,并综合初至折射波走时特征获得了各测线的速度结构和界面构造特征。文中选取SS04-1和SS11-2测线,对其探测结果进行了详细的介绍,由这2条测线各自确定的主要地层界面和构造特征都与测线上的钻探资料具有较好的一致性。文中的探测结果表明:在城市活断层的探测研究中,对于反射波法勘探难以开展的地区,高分辨折射波法勘探技术不失为一种有效的替代方法。

关键词: 城市活断层探测, 高分辨地震折射波法, 兰州市