Reliable monitoring of unstable rock slopes is a prerequisite for successful mitigation of landslide hazards. However, most state‐of‐the art techniques rely on measuring the local surface displacement in the potential release area. In contrast, recording ambient vibration data allows for analyzing structural dynamic parameters of the unstable slope, such as resonance frequency, polarization of vibration, and energy dissipation. These parameters can be linked to properties of the instability, for example, to rock stiffness and fracture network orientation. We developed a processing method for continuous seismic data based on enhanced frequency domain decomposition modal analysis and applied it to the unstable rock slope Preonzo in Switzerland (∼140,000 m³). Four years of ambient vibration data recorded at two permanent seismometers on the instability were analyzed, providing the resonance frequency, damping ratio, and normal mode shapes of the fundamental (∼3.5 Hz) and the first higher (∼4.2 Hz) vibrational mode. We found that modal analysis can be reliably used to monitor the dynamic response of an unstable rock slope. We observed annual changes of all parameters with a damping ratio varying between 6.0% and 9.7% for the fundamental mode. The dynamic parameters appear to be primarily driven by temperature and only secondarily by opening and closing of fractures. No large slope failure was registered during the observation period. However, the data provide a baseline model for ongoing slope monitoring to recognize structural changes before a future collapse. The setup proposed builds a complementary monitoring system to displacement‐based surveying.

中文翻译：

---

使用共振模式分析监测Preonzo岩石边坡失稳

可靠地监测不稳定的岩石边坡是成功减轻滑坡灾害的先决条件。但是，大多数最先进的技术都依赖于测量潜在释放区域中的局部表面位移。相反，记录环境振动数据可以分析不稳定斜坡的结构动力学参数，例如共振频率，振动极化和能量耗散。这些参数可以与不稳定性的属性关联，例如，与岩石刚度和裂缝网络方向关联。我们开发了一种基于增强频域分解模态分析的连续地震数据处理方法，并将其应用于瑞士Preonzo不稳定岩质边坡（〜140,000 m ³）。分析了在两个永久性地震仪上记录的关于不稳定性的四年环境振动数据，提供了共振频率，阻尼比以及基本振动模式（约3.5 Hz）和第一个较高振动模式（约4.2 Hz）的正常模式形状。我们发现模态分析可以可靠地用于监测不稳定岩石边坡的动力响应。对于基本模式，我们观察到所有参数的年度变化，阻尼比在6.0％和9.7％之间。动态参数似乎主要由温度驱动，其次仅由裂缝的打开和闭合驱动。在观察期间没有发现大的边坡破坏。但是，这些数据为进行中的边坡监测提供了基线模型，以便在未来坍塌之前识别结构变化。