Microtremor Survey Techniques for Disclosing Stratigraphic Characteristics in the Platform on the Chinese Loess Plateau
摘要
The Chinese Loess Plateau (CLP) is prone to various geological hazards because the loess is characterized by loose sediment, water sensitivity, and extremely thick coverage. Thus, seeking a convenient technique to reveal near-surface geological structures effectively is of great significance for mitigating the loess geohazards in the CLP. However, given the complex structures and surface conditions in the loess area, traditional geophysical methods often face numerous limitations. In contrast, we employed a method with lower terrain requirements and stronger anti-interference capabilities. We selected the Heifangtai Terrace as the test site of the loess platform, which contains complete stratigraphic units of the CLP and is also a typical region with different loess landslides. We used the Extended Spatial Autocorrelation (ESPAC) and Horizontal-to-Vertical Spectral Ratio (HVSR) methods to detect the stratigraphic structure of the study area. The accuracy of these methods was verified using in-situ borehole, outcrop, and geological profile information. Our results show that the ESPAC method provides precise stratigraphic division, while the HVSR method enables rapid identification of the boundary between loose sediment and bedrock. Additionally, high-resolution ESPAC can serve as a substitute for boreholes to assist HVSR observations in constructing the resonance frequency-sediment thickness relationship for the area. Therefore, the integrated microtremor survey technology provides a rapid and cost-effective approach to acquire reliable stratigraphic information, highlighting its utility in geological hazard mitigation.