To predicting the landslide ability of sandy soil around the riverbank area, a field test for the vibration propagation of the ground surface at different positions from a fixed vibration excitation was performed near the river. While the current standards for ground vibration focus on predicting the vibration amplitude, this paper studies the frequency content. By analyzing the vibration response in all three directions under impact loads that are susceptible to resonance, the natural frequencies were extracted to evaluate the characteristics of the ground. Then, a novel indication for landslide is presented based on the appearance of natural frequencies in each vibration direction. The effectiveness and suitability of this evidence based on the transmission capacity and matched vibration model. It is showed that the vibration response of the ground weakens not only with a decrease in frequency when stiffness of soil reduce but also with an increase in the number of frequencies when soil layers lose cohesion. This study provides reference for disaster prevention agencies and for construction planning along river areas.