Associate Professor XU Peifen and her team collect and analyze microtremor data from eight observation sites using a microtremor-array survey method. The eight microtremor observation sites are located throughout the Fengtai Sag, Laiguangying High, and Houshayu Sag. Traditional geophysical or geological survey methods are not effective in these areas due to the heavy traffic and dense buildings in the highly populated urban area. They utilize the microtremor-exploration method at the eight observation sites to estimate the thick of Cenozoic sediments (or the bed rock depth) based on the shear-wave velocity profiles obtained through the surface-wave dispersion analysis. 

Integrating the existing drilling results and other geological data from the area, they successfully obtained the bedrock depth, which plays a significant role in interpreting the thickness of the Cenozoic. They also demonstrated that increased data density may lead to an improved accuracy in bedrock depth mapping. It has been shown that this method is especially useful and effective in densely populated urban areas where heavy traffic and various sources of noises exist, such as in Beijing. The information is deemed very useful for understanding the geological structures, regional tectonics, and practical geotechnical problems involved in civil geological engineering in and around Beijing City.