Study on Long-Period Ground Motion Amplification Effect of Buried Paleogene Basin Structures in North China

A significant number of geological profiles showed thick Quaternary and Neoproterozoic systems in the North China Plain. They also reveal basin structures from the Paleoproterozoic era. These structures extend over 100 km in length and span several kilometers in depth. In this paper, we establish a "two concave and one convex" basin tectonic model based on the latest data from urban active fault detection and basin tectonic patterns identified in North China. Using the finite difference method, we simulate and analyze the effects of their long-period ground shaking. The "vertical model" and "parallel model" display stronger amplification of long-period ground shaking than the regular model unaffected by submerged basin tectonics. The amplification varies across space and different time periods in both models. These suggest that the angle between the tectonic axis of the subduction basin and the rupture direction of the earthquake source may be a key factor in evaluating long-period ground shaking amplification in subduction basin structures. The analysis of spectral ratios indicates that subduction basin tectonics can amplify the peak ground shaking up to three times. The amplification could last for certain periods within a specific epicentral distance range. Such an amplification effect is significant for seismic hazard risk assessment and cannot be overlooked. This study provides a reference for future urban seismic hazard risk analysis in North China.