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Abstract. The increasing hazard of major rock slope failures, exacerbated by climate change, underscores the importance of anticipating pre-failure process dynamics. While standard triggers are recognized for small rockfalls, few comprehensive driver quantifications exist for massive pre-failure rock slopes. Here we exploit >4 years multi-method high-resolution monitoring data from a well-prepared high-magnitude rock slope instability. To quantify and understand the effect of possible drivers – water from rain and snowmelt, internal rock fracturing and earthquakes – we correlate slope displacements with environmental data, local seismic recordings and earthquake catalogues. During the snowmelt phase, displacements are controlled by meltwater infiltration with high correlation and a time lag of 4–9 days. During the snow-free summer, rainfall drives the system with a time lag of 1–16 h for up to several days without a minimum activation rain sum threshold. Detected rock fracturing, linked to temperature and freeze-thaw cycles, is predominantly surface-near and unrelated to displacement rates. A classic Newmark analysis of recent and historic earthquakes indicates a low potential for immediate triggering of a major failure at the case site, unless it is already very close to failure. Seismic topographic amplification of the peak ground velocity at the summit ranges from a factor of 2–11 and is spatially heterogeneous, indicating a high criticality of the slope. The presented methodological approach enables a comprehensive rockfall driver evaluation and indicates where future climatic changes, e.g. in precipitation intensity and frequency, may alter the preparation of major rock slope failures.
Leinauer et al. (Fri,) studied this question.