Abstract
The stability of rock slopes is often guided significantly by the structural geology of the rocks composing the slope. In this work, we analysed the influences of structural characteristics, and of their seismic responses, on large and deep-seated rock slope failure development. The study was focused on the Tamins and Fernpass rockslides in the European Alps and on the Balta and Eagle’s Lake rockslides in the southeastern Carpathians. These case studies were compared with catastrophic rock slope failures with ascertained or very likely seismic origin in the Tien Shan Mountains. The main goals was to identify indicators for seismically-induced rock slope failures based on the source zone rock structures and failure scar geometry. We present examples of failures in anti-dip slopes and along-strike rock structures that were potentially (or partially) caused by seismic triggering, and we also considered a series of mixed structural types, which are more difficult to interpret conclusively. Our morpho-structural study was supported by distinct element numerical modelling that showed that seismic shaking typically induces deep-seated deformation in initially “stable” rock slopes. In addition, for failures partially triggered by dynamic shaking, these studies can help identify the contribution of the seismic factor to slope instability. The identification of the partial seismic origin on the basis of the dynamic response of rock structures can be particularly interesting for case histories in less seismically active mountain regions (in comparison with the Andes, Tien Shan, Pamirs), such as in the European Alps and the Carpathian Mountains.
Highlights
Rockslides occur in many mountain regions of the world [1,2,3,4,5,6] and are defined as large, mostly translational bedrock landslides including large volumes of debris [7,8,9]
We review the structural features of the source zones of selected case studies that could indicate a seismic trigger for these large rock slope failures
In this paper we presented structural geology information for several rockslides which display some characteristics of seismic triggering: they present a very deep scarp high on the slope, do not appear to have been influenced by river undercutting, and seem to have been formed in a statically stable condition
Summary
Rockslides occur in many mountain regions of the world [1,2,3,4,5,6] and are defined as large, mostly translational bedrock landslides including large volumes of debris (up to billions m3 ) [7,8,9]. The exact cause of slope failure (if prehistorical) is often unclear. They can be triggered by several and diverse factors, and most of the time there is not a single cause but rather a combination of geological, morphological, physical, and/or human factors that prepare a slope for failure. We distinguish trigger (near-immediate causes of a slope failure) and preparatory or preconditioning factors (background conditions and long-term actions). Whereas the definition of landslide sizes is discussed in various works in relation to their debris volume or slope height, e.g., Davies and McSaveney [10] and. The presented massive rock slope failures are influenced by factors that condition slope instability depending on the Geosciences 2020, 10, 323; doi:10.3390/geosciences10080323 www.mdpi.com/journal/geosciences
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