The relationship between rock-slope failure and glacier retreat is complex, and paraglacial failures often lack clearly identified triggers. To better understand the role of glacier retreat in rock-slope failures, we analysed the processes that led to the October 1967 Grewingk landslide in Kachemak Bay State Park on the Kenai Peninsula, Southcentral Alaska. The rock material collapsed onto the glacier toe and into its pro-glacial lake and produced a tsunami wave that swept the outwash plain. On the day of the failure, rainfall and snowmelt were well within normal ranges, and seismic records show no significant shaking. Three years prior to the 1967 failure, the slope withstood the second largest earthquake ever recorded (Great Alaskan earthquake, M_W 9.2). We reassessed the volume of the failure by differencing pre- and post-digital terrain models and found a value of 20–24 × 10⁶ m³, which is four times smaller than a previous estimate. The back analysis of the Grewingk landslide is based on remote sensing data and field measurements including aerial satellite image analysis, detailed surveying and understanding of the structural geology, a kinematic analysis, and runout modelling. Our research provides an example of a major paraglacial failure that lacks an obvious trigger and points to several geological factors and changing environmental conditions that likely promote such failures. This study further indicates that the Grewingk landslide, pre-conditioned by the geometry of faults and joints, may have reached a critical stability state due to internal processes and the potential combined effects of seismic activity and glacier retreat prior to the collapse.

Brittle faults and fault zones are among the most hydraulically active elements in predominantly impermeable crystalline host rock. They pose a significant challenge to underground infrastructure like nuclear waste repositories. Brittle fault zones frequently occur along pre-existing ductile shear zones as they introduce weakness planes in the rock.Four brittle fault zones of ductile origin were analyzed in the Rotondo Granite at the “BedrettoLab” in the Swiss Central Alps. Scanline mapping, rock sampling and permeability measurements using three different methods provide detailed insights into the heterogeneous fault zone architecture and hydrogeology. Average intact rock permeability is in the range of 10⁻¹⁹ to 10⁻¹⁷ m². Fluid flow is channeled into single open or partially mineralized fractures of, at point-scale, up to 10⁻¹⁴ m², demonstrated by selective gas probe permeameter measurements and borehole hydraulic testing. Reduced permeabilities have been measured in close proximity to these permeable features, indicating alteration of and around the fracture walls.

Understanding in situ stress magnitudes and orientations is critical for the design of underground engineering projects, including tunnels, geological nuclear waste repositories, and enhanced geothermal systems (EGS). This study presents the results of a regional 3D numerical stress model developed using FLAC3D, created to analyze stress variations along the Bedretto Tunnel in the southern Switzerland. The Bedretto Tunnel is a new underground research facility designed to host in situ experiments related to deep geothermal energy utilization, earthquake physics, and tunneling, with each field relying on robust estimates of stress magnitudes and orientations. The model considers the effects of topography, active tectonic stresses, and rock properties to assess local and regional stress patterns. The model is first calibrated against local in situ stress measurements obtained via the mini-frac method conducted near the BedrettoLab. By evaluating the characteristics of the excavation damage zone (EDZ) around the Bedretto Tunnel, we were able to further validate the simulated stress states along the tunnel. After calibration, we analyze the in situ stress variations in the surrounding area to evaluate the impact of topography and active stress on the local stress distribution. Modeling results reveal that stress magnitudes and orientations along the tunnel are strongly influenced by topography and tectonic forces, transitioning from strike-slip faulting near the portal (TM 0-1900) to normal faulting (TM 1900-5200). The results also show that topography influences stress orientation: at shallow to intermediate depths (up to 1.5 km), principal stresses are non-vertical, transitioning to more vertical and horizontal orientations at greater depths. The results indicate that the K-ratio (horizontal to vertical stress) depends on topography, exhibiting a wide range at shallow depths and tending toward unity at greater depths. Although the modeling results capture the overall variations of the stress state in the Bedretto region and can serve as a potential base model in this region, the local stress heterogeneity observed from in situ stress measurements could not be modeled, highlighting the necessity of incorporating geological structures, including faults and fractures, as well as tunnel-induced perturbations.

One major hurdle for understanding earthquake mechanics are observational limitations. Important phenomena like strain localisation, fault dilation, and fault healing are readily studied in rock mechanical laboratory experiments and with numerical models. At the scale of natural earthquakes, however, these phenomena are often unresolvable, even by state-of-the-art observatories. To overcome this limitation, we are currently building the Earthquake Physics Testbed at the Bedretto Underground Laboratory for Geosciences and Geoenergies (BedrettoLab), an experimental testbed where we can activate an extensively instrumented natural fault zone via hydraulic stimulation. The goal of the Fault Activation and Earthquake Rupture (FEAR) project is to induce earthquakes of up to Mw~1.0 on this exceptionally well characterised and instrumented fault zone. Here we summarize the main scientific goals and current FEAR project status, and present first results from conducted experiments. We discuss how this large-scale experimental approach may allow us to tackle both fundamental science as well as practical questions on earthquake physics, induced seismicity and seismic hazard.

Slope instability poses significant challenges in geotechnical engineering, necessitating effective mitigation strategies. Among these strategies, toe buttressing has emerged as a prominent method, involving the strategic placement of materials at the base of unstable slopes. However, the efficacy of toe buttressing remains insufficiently explored in scientific literature, particularly through the integration of real-time monitoring and numerical modeling. This paper explores the effectiveness of toe buttressing as mitigation measure for slope stability without the influence of additional stabilization methods. Through a combination of field monitoring, laboratory testing, and the finite element analysis, we assess the influence of toe buttressing on slope dynamics and stability under varying environmental conditions. The study site, located in a basalt quarry in Nentershausen, Germany, experienced a landslide, with the sliding plane located at the interface between basalt formations and the underlying clay layers. Our monitoring results demonstrate that the placement of a 10 m thick toe buttress effectively halted the movement of a 295,000 m³ landslide. Additionally, we investigated the impact of different buttress configurations and groundwater levels on the factor of safety (FoS) using a 2D finite element model. The results clearly show the important role that toe buttresses play in strengthening slope stability. Our study emphasizes the need for more detailed case studies focusing solely on toe buttressing as a means of stabilization. Such research is essential to develop statistical models that can determine the necessary buttress volume and height to support/stabilize different landslide scenarios. Additionally, we discuss the broader implications of our study and future research for slope management applications and underscore the need for interdisciplinary approaches to address the complexities of slope stability in a changing environment.