关键词: 城市活断层, 断层活动性, 地震危险性评价

Abstract: According to the practice of urban active fault exploration and associated activity assessment conducted in recent years,this paper summarizes the problems encountered in geological,geomorphological,geochemical and geophysical explorations,and proposes the following means and suggestions to solve these problems.To determine the most recent faults or fault zones,emphases should be placed on iden～tifing the youngest active faults and offset geomorphology.To understand the history of faulting and to discover the last offset event,it is suggested to combine geophysical prospecting,drilling and trenching into one profile.Because of significant uncertainties in late Quaternary dating,it is advised to sample systematically and to use multiple dating methods.Shallow seismic reflection has been proven to be the most useful method in urban active fault exploration.However,it is a pressing need to increase the quality of data acquiring and data processing to obtain high resolution images,so that the abi～lity of identifying active faults could be enhanced.Combination of seismic P-wave reflection and S-wave reflection methods is proved to be a powerful means to investigate tectonic environments of deep crust.

Key words: urban active fault, activity of fault, seismic risk assessment