Site classification scheme based on geological age and genesis for Xinjiang and the Capital Metropolitan areas of China

The site classification map is one of the vital inputs in earthquake disaster scenario prediction and risk modeling that provides a perspective of proxy-based methods. In China, a systematic empirical relationship between geological age, genesis, and site class in the practice of site classification has yet to be established. In this study, data from 1:500,000 geological maps and thousands of engineering boreholes in the Xinjiang Uygur Autonomous Region and the Capital Metropolitan area in China were collected, and different types of geological unit were classified according to 10 types of geological age and 18 types of geological genesis. A site classification scheme was proposed on the basis of geological age, geological genesis, statistical properties of boreholes, and lithological descriptions. Borehole characteristics were investigated in terms of their proportions among the different site classes, and the mean and standard deviation of V S30. Accordingly, a chart correlating four site classes (B, C, D, and E) with each type of geological age and genesis was developed that could be used as a practical tool in regional site classification. Site classification maps were delineated in both areas using the proposed scheme and compared with those derived from the topographic slope-proxy method and another geology-proxy method, and the results showed that it is effective in identifying the site class, especially for class E sites, and probably class B that inferred by the qualitative evaluation. Moreover, the applicability of the method has also been confirmed in areas outside the study area. It is anticipated that it could provide a technical template for nationwide site classification using geological maps.