scholarly journals Locating rock slope failures along highways and understanding their physical processes using seismic signals

2021 ◽  
Vol 9 (3) ◽  
pp. 505-517
Author(s):  
Jui-Ming Chang ◽  
Wei-An Chao ◽  
Hongey Chen ◽  
Yu-Ting Kuo ◽  
Che-Ming Yang
Keyword(s):  
Slope Failure ◽  
Rock Slope ◽  
Scaling Law ◽  
Mass Movement ◽  
Volume Estimation ◽  
Seismic Signals ◽  
Slope Failures ◽  
Physical Processes ◽  
Seismic Parameters ◽  
Duration Magnitude

Abstract. Regional monitoring of rock slope failures using the seismic technique is rarely undertaken due to significant source location errors; this method also still lacks the signal features needed to understand events of this type because of the complex mass movement involved. To better comprehend these types of events, 10 known events along highways in Taiwan were analyzed. First, a hybrid method (GeoLoc) composed of cross-correlation-based and amplitude-attenuation-based approaches was applied, and it produced a maximum location error of 3.19 km for the 10 events. We then analyzed the ratio of local magnitude (ML) and duration magnitude (MD) and found that a threshold of 0.85 yields successful classification between rock slope failure and earthquake. Further, GeoLoc can retrieve the seismic parameters, such as signal amplitude at the source (A0) and ML of events, which are crucial for constructing scaling law with source volume (V). Indeed, Log(V) = 1.12 ML + 3.08 and V = 77 290 A00.44 derived in this study provide the lower bound of volume estimation, as the seismic parameters based on peak amplitudes cannot represent the full process of mass loss. Second, while video records correspond to seismic signals, the processes of toppling and sliding present column- and V-shaped spectrograms, respectively. The impacts of rockfall link directly to the pulses of seismic signals. Here, all spectrogram features of events can be identified for events with volumes larger than 2000 m3, corresponding to the farthest epicenter distance of ∼ 2.5 km. These results were obtained using the GeoLoc scheme for providing the government with rapid reports for reference. Finally, a recent event on 12 June 2020 was used to examine the GeoLoc scheme's feasibility. We estimated the event's volume using two scalings: 3838 and 3019 m3. These values were roughly consistent with the volume estimation of 5142 m3 from the digital elevation model. The physical processes, including rockfall, toppling, and complex motion behaviors of rock interacting with slope inferred from the spectrogram features were comprehensively supported by the video record and field investigation. We also demonstrated that the GeoLoc scheme, which has been implemented in Sinwulyu catchment, Taiwan, can provide fast reports, including the location, volume, and physical process of events, to the public soon after they occur.

scholarly journals Locating rock slope failures along highways and understanding their physical processes using seismic signals

2020 ◽  
Author(s):  
Jui-Ming Chang ◽  
Wei-An Chao ◽  
Hongey Chen ◽  
Yu-Ting Kuo ◽  
Che-Ming Yang
Keyword(s):  
Rock Slope ◽  
Scaling Law ◽  
Mass Movement ◽  
Hybrid Approach ◽  
Volume Estimation ◽  
Seismic Signals ◽  
Slope Failures ◽  
Physical Processes ◽  
Seismic Parameters ◽  
Duration Magnitude

Abstract. Regional monitoring of rock slope failures by the seismic technique is rarely studied due to significant source location errors, and it still lacks the signal features needed for understanding events of this type because of the complex mass movement involved. To better understand events of this type, ten known events along highways in Taiwan were analyzed. First, a hybrid approach (GeoLoc) composed of cross-correlation-based and amplitude-attenuation-based approaches was applied, and it produced a location error of maximum 3.19 km for the ten events. Then, we analyzed the ratio of local magnitude (ML) and duration magnitude (MD) and found that a threshold of 0.85 yields successful classification between rock slope failure and earthquake. Further, the GeoLoc can retrieve the seismic parameters, such as signal amplitude at the source (A0) and ML of events, which are crucial for constructing scaling law with source volume (V). Indeed, Log(V) = 1.12 ML + 3.08 and V = 77,290 A00.44 derived in this study provide the lower bound of volume estimation, since the seismic parameters based on peak amplitudes cannot represent the full process of mass loss. Second, while video records correspond with seismic signals, the processes of toppling and sliding present column- and V-shaped spectrograms, respectively. The impacts of rockfall directly link directly to the pulses of seismic signals. Here, all spectrogram features of events can be identified by event volumes larger than 2,000 m3, corresponding to the farthest epicenter distance ~2.5 km. The previous results were obtained using the GeoLoc scheme for providing the government rapid reports for reference. Finally, a recent event on 12th June 2020 was used to examine the GeoLoc scheme’s feasibility. We estimated the event's volume by the two scalings: 3,838 m3 and 3,019 m3, which was roughly consistent with the volume estimation of 5,142 m3 from the digital elevation model. The physical processes, including rockfall, toppling, and complex motion behaviors of rock interacting with slope inferred from the spectrogram features were comprehensively supported by the video record and field investigation. We also demonstrated that the GeoLoc scheme, which has been implemented in Sinwulu catchment, Taiwan, can provide fast reports, including the location, volume, and physical process of events of this type to the public soon after they occur.

Recurrent rock avalanches progressively dismantle mountain ridges in the Longmen Shan, China, most recently in the 2008 Wenchuan earthquake

2021 ◽  
Author(s):  
Janusz Wasowski ◽  
Maurice McSaveney ◽  
Luca Pisanu ◽  
Vincenzo Del Gaudio ◽  
Yan Li ◽  
...  
Keyword(s):  
Wenchuan Earthquake ◽  
Ambient Noise ◽  
Slope Failure ◽  
Mass Movement ◽  
Rock Avalanche ◽  
Ground Vibration ◽  
Source Area ◽  
Slope Failures ◽  
Rock Avalanches ◽  
Beichuan County

<p>Large earthquake-triggered landslides, in particular rock avalanches, can have catastrophic consequences. However, the recognition of slopes prone to such failures remains difficult, because slope-specific seismic response depends on many factors including local topography, landforms, structure and internal geology. We address these issues by exploring the case of a rock avalanche of >3 million m<sup>3</sup> triggered by the 2008 Mw7.9 Wenchuan earthquake in the Longmen Shan range, China. The failure, denominated Yangjia gully rock avalanche, occurred in Beichuan County (Sichuan Province), one of the areas that suffered the highest shaking intensity and death toll caused by co-seismic landsliding. Even though the Wenchuan earthquake produced tens of large (volume >1 million m<sup>3</sup>) rock avalanches, few studies so far have examined the pre-2008 history of the failed slope or reported on the stratigraphic record of mass-movement deposits exposed along local river courses. The presented case of the Yangjia gully rock avalanche shows the importance of such attempts as they provide information on the recurrence of large slope failures and their associated hazards. Our effort stems from recognition, on 2005 satellite imagery, of topography and morphology indicative of a large, apparently pre-historic slope failure and the associated breached landslide dam, both features closely resembling the forms generated in the catastrophic 2008 earthquake. The follow-up reconstruction recognizes an earlier landslide deposit exhumed from beneath the 2008 Yangjia gully rock avalanche by fluvial erosion since May 2008. We infer a seismic trigger also for the pre-2008 rock avalanche based on the following circumstantial evidence: i) the same source area (valley-facing, terminal portion of a flat-topped, elongated mountain ridge) located within one and a half kilometer of the seismically active Beichuan fault; ii) significant directional amplification of ground vibration, sub-parallel to the failed slope direction, detected via ambient noise measurements on the ridge adjacent to the source area of the 2008 rock avalanche and iii) common depositional and textural features of the two landslide deposits. Then, we show how, through consideration of the broader geomorphic and seismo-tectonic contexts, one can gain insight into the spatial and temporal recurrence of catastrophic slope failures  in Beichuan County and elsewhere in the Longmen Shan. This insight, combined with local-scale geologic and geomorphologic knowledge, may guide selection of suspect slopes for reconnaissance, wide-area ambient noise investigation aimed at discriminating their relative susceptibility to co-seismic catastrophic failures. We indicate the feasibility of such investigations through the example of this study, which uses 3-component velocimeters designed to register low amplitude ground vibration.</p>

scholarly journals Rockfall induced seismic signals: case study in Montserrat, Catalonia

2008 ◽  
Vol 8 (4) ◽  
pp. 805-812 ◽  
Author(s):  
I. Vilajosana ◽  
E. Suriñach ◽  
A. Abellán ◽  
G. Khazaradze ◽  
D. Garcia ◽  
...  
Keyword(s):  
Particle Motion ◽  
Mass Movement ◽  
Seismic Energy ◽  
Quantitative Information ◽  
Volume Estimation ◽  
Seismic Signals ◽  
Energy Estimation ◽  
Time Frequency ◽  
On The Road ◽  
The Impact

Abstract. After a rockfall event, a usual post event survey includes qualitative volume estimation, trajectory mapping and determination of departing zones. However, quantitative measurements are not usually made. Additional relevant quantitative information could be useful in determining the spatial occurrence of rockfall events and help us in quantifying their size. Seismic measurements could be suitable for detection purposes since they are non invasive methods and are relatively inexpensive. Moreover, seismic techniques could provide important information on rockfall size and location of impacts. On 14 February 2007 the Avalanche Group of the University of Barcelona obtained the seismic data generated by an artificially triggered rockfall event at the Montserrat massif (near Barcelona, Spain) carried out in order to purge a slope. Two 3 component seismic stations were deployed in the area about 200 m from the explosion point that triggered the rockfall. Seismic signals and video images were simultaneously obtained. The initial volume of the rockfall was estimated to be 75 m3 by laser scanner data analysis. After the explosion, dozens of boulders ranging from 10−4 to 5 m3 in volume impacted on the ground at different locations. The blocks fell down onto a terrace, 120 m below the release zone. The impact generated a small continuous mass movement composed of a mixture of rocks, sand and dust that ran down the slope and impacted on the road 60 m below. Time, time-frequency evolution and particle motion analysis of the seismic records and seismic energy estimation were performed. The results are as follows: 1 – A rockfall event generates seismic signals with specific characteristics in the time domain; 2 – the seismic signals generated by the mass movement show a time-frequency evolution different from that of other seismogenic sources (e.g. earthquakes, explosions or a single rock impact). This feature could be used for detection purposes; 3 – particle motion plot analysis shows that the procedure to locate the rock impact using two stations is feasible; 4 – The feasibility and validity of seismic methods for the detection of rockfall events, their localization and size determination are comfirmed.

scholarly journals Monitoring of recent mass movement activity in anthropogenic slopes of the Krušné Hory Mountains (Czech Republic)

2011 ◽  
Vol 11 (5) ◽  
pp. 1463-1473 ◽  
Author(s):  
J. Burda ◽  
L. Žižka ◽  
J. Dohnal
Keyword(s):  
Czech Republic ◽  
Slope Failure ◽  
Water Saturation ◽  
Mass Movement ◽  
Interdisciplinary Approach ◽  
Open Pit ◽  
Mass Movements ◽  
Slope Failures ◽  
The Czech Republic ◽  
Krušné Hory Mountains

Abstract. Recent mass movements currently comprise one of the main morphogenetic processes in the extensive anthropogenic relief of the foreground of the Krušné Hory Mountains in the Czech Republic. These mass movements result in several types of deep-seated slope failures, depending on the type of movement and the water saturation of the landslide material. This paper presents the results of a detailed geomorphic survey and orthophotograph analysis combined with geodetic monitoring data in an area affected by open-pit coal mining. An interdisciplinary approach has enabled an in-depth review of both the dynamics and development of recent slope failures. The article describes deep-seated landslide complex in this part of the foothills of the Krušné Hory Mountains. At the study site, mass movements occur in thick colluvial mantle and weathered Tertiary claystones. The main factors influencing their development include rainfall culminations, groundwater flowing from the valley of Šramnický Brook and former slope failures. All of the slope failures that have occurred here have originated at former slope failure sites.

Process dynamics, real time monitoring and early warning at an imminent cliff fall (Hochvogel, Allgäu Alps)

2020 ◽  
Author(s):  
Johannes Leinauer ◽  
Benjamin Jacobs ◽  
Michael Krautblatter
Keyword(s):  
High Resolution ◽  
Early Warning ◽  
Slope Failure ◽  
Rock Slope ◽  
Point Clouds ◽  
Aerial Images ◽  
Slope Failures ◽  
High Resolution Data ◽  
Process Dynamics ◽  
Resolution Data

<p>Costs for (re)installation and maintenance of protective structures are increasing while alpine hazards progressively threaten alpine communities, infrastructure and economics. With climatic changes, anticipation and clever early warning of rock slope failures based on the process dynamics become more and more important. The imminent rock slope failure at the Hochvogel summit (2592 m a.s.l., Allgäu Alps) offers a rare possibility to study a cliff fall at a high alpine carbonate peak during its preparation and until failure. In this real case scenario, we can develop and test an operative and effective early warning system.</p><p>The main cleft is two to six metres wide at the summit and at least 60 metres deep at the sides. Several lateral cracks are opening at faster pace and separate different instable blocks. 3D-UAV point clouds reveal a potentially failing mass of 260,000 m³ in six subunits. However, the pre-deformation is yet not pronounced enough to decide on the expected volume. Analysis of historical ortho- and aerial images yields an elongation of the main crack length from 10 to 35 m from 1960 until now. Discontinuous tape extensometer measurements show 35 cm opening of the main cleft between 2014 and 2020 with movement rates up to 1 cm/month. Since July 2018, automatic vibrating wire gauges deliver high-resolution data to an online server. In October 2019, we transferred the system into LoRa with data transmission every 10 min. Automatic warnings via SMS and email are triggered when crossing specific thresholds.</p><p>Here we demonstrate long-term process dynamics and 2-years of high-resolution data of a preparing alpine rock slope failure. Corresponding geodetic, photogrammetric, seismic and gravimetric measurements complete the comprehensive measurement design at the Hochvogel. This will help to decipher anticipative signals of initiating alpine rock slope failures and improve future event predictions.</p>

scholarly journals Paraglacial rock-slope deformations: sudden or delayed response? Insights from an integrated numerical modelling approach

Landslides ◽  
2020 ◽  
Author(s):  
Margherita Cecilia Spreafico ◽  
Pietro Sternai ◽  
Federico Agliardi
Keyword(s):  
Numerical Modelling ◽  
Slope Failure ◽  
Rock Slope ◽  
Rock Slope Stability ◽  
Major Influence ◽  
Delayed Response ◽  
Catastrophic Failure ◽  
Slope Failures ◽  
Ice Dynamics ◽  
Modelling Approach

Abstract Glacial and paraglacial processes have a major influence on rock slope stability in alpine environments. Slope deglaciation causes debuttressing, stress and hydro-mechanical perturbations that promote progressive slope failure and the development of slow rock slope deformation possibly evolving until catastrophic failure. Paraglacial rock slope failures can develop soon after or thousands of years after deglaciation, and can creep slowly accelerating until catastrophic failure or nucleate sudden rockslides. The roles of topography, rock properties and deglaciation processes in promoting the different styles of paraglacial rock slope failure are still elusive. Nevertheless, their comprehensive understanding is crucial to manage future geohazards in modern paraglacial settings affected by ongoing climate change. We simulate the different modes and timing of paraglacial slope failures in an integrated numerical modelling approach that couples realistic deglaciation histories derived by modelling of ice dynamics to 2D time-dependent simulations of progressive failure processes. We performed a parametric study to assess the effects of initial ice thickness, deglaciation rate, rock-slope strength and valley shape on the mechanisms and timing of slope response to deglaciation. Our results allow constraining the range of conditions in which rapid failures or delayed slow deformations occur, which we compare to natural Alpine case studies. The melting of thicker glaciers is linked to shallower rockslides daylighting at higher elevation, with a shorter response time. More pronounced glacial morphologies influences slope lifecycle and favour the development of shallower, suspended rockslides. Weaker slopes and faster deglaciations produce to faster slope responses. In a risk-reduction perspective, we expect rockslide differentiation in valleys showing a strong glacial imprint, buried below thick ice sheets during glaciation.

Structural geology of large (ancient) rockslides - an indicator for a seismic or climatic origin?

2020 ◽  
Author(s):  
Emilie Lemaire ◽  
Anne-Sophie Mreyen ◽  
Hans-Balder Havenith
Keyword(s):  
Structural Geology ◽  
Rock Slope ◽  
Structural Characteristics ◽  
Mass Movement ◽  
Source Zone ◽  
Slope Failures ◽  
Study Results ◽  
The Alps ◽  
The Stability ◽  
Seismic Origin

<p>The stability of rock slopes is often guided by the structural geology of the rocks composing the slope. Geological structures, such as ductile folds, discontinuities as well as brittle faults and fractures, are known factors contributing to a decrease in slope stability according to their orientation in space - with respect to the general orientation of the main slope and its (seismo-) tectonic damage history. Additionally, a rock slope may undergo many forms of gravitationallyinduced, erosional and/or weathering-induced destabilisation.</p><p>Rock slope failures may be classified and described according to several factors, such as their volume, displacement mechanisms and velocity. In this work, especially deep-seated and very large failures (with a volume of >10<sup>7</sup> m<sup>3</sup>) are analyzed with regard to their structural characteristics.</p><p>Giant rockslides originate as planar, rotational, wedge, compound, or irregular slope failures. Most of them convert into flow-like rock avalanches during emplacement. Here, we will not detail the evolution of rock slope failures but rather focus on their origin. The main goal is to identify features allowing to distinguish seismic trigger modes from climatic ones, notably on the basis of the source zone rock structures. We will present examples of classical anti-dip slope (and along-strike) rock structures that hint at a seismic origin, but we will also consider a series of mixed structural types, which are more difficult to interprete. This morpho-structural study is supported by numerical modelling results showing that seismic shaking typically induces deeper seated deformation in initially ‘stable’ rockslopes.</p><p>For failures only partially triggered by dynamic shaking, these study results could help to identify the seismic factor in slope evolution. Especially in less seismically active mountain regions, such as the Alps and the Carpathian Mountains, these analyses can be used for paleoseismic studies – provided that dating the seismic initiation of mass movement is possible. For instance, we will show that the “Tamins” and the “Fernpass” rockslides in the Alps present structural and morphological features hinting at a partly seismic origin. Furthermore, we present study cases of ancient rockslides in the SE Carpathians (“Balta” and “Eagle’s Lake”), where a pure seismic origin is most probable and currently under discussion (supported by numerical analyses).</p>

scholarly journals Analysis of the Influence of Structural Geology on the Massive Seismic Slope Failure Potential Supported by Numerical Modelling

Geosciences ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 323
Author(s):  
Emilie Lemaire ◽  
Anne-Sophie Mreyen ◽  
Anja Dufresne ◽  
Hans-Balder Havenith
Keyword(s):  
Structural Geology ◽  
Numerical Modelling ◽  
Slope Failure ◽  
Rock Slope ◽  
Tien Shan ◽  
Source Zone ◽  
European Alps ◽  
Rock Slopes ◽  
Slope Failures ◽  
Seismic Origin

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.

scholarly journals Does climate change influence the frequency of large rock slope failures?

2020 ◽  
Author(s):  
Simon Loew ◽  
Nora Buehler ◽  
Jordan Aaron
Keyword(s):  
Slope Failure ◽  
Rock Slope ◽  
Negative Temperature ◽  
Climatic Conditions ◽  
Swiss Alps ◽  
Rock Fall ◽  
Mean Annual Temperature ◽  
European Alps ◽  
Depth Range ◽  
Slope Failures

<p>A large number of scientific contributions (e.g. BAFU 2017, Speicher 2017, Phillips et al. 2017, Ravanel et al. 2017, Haque et al. 2016) have suggested that many recent rock slope failures in the European Alps have been triggered by climate warming. For example, Huggel et al. 2012 and Fischer et al. 2012 could show that rock fall frequencies above 2000 masl increased significantly since 1990 at regional (Swiss Alps and adjacent areas) and local (Mont Blanc) scale, based on 52 events larger than 1000 m<sup>3</sup> (PERMOS data base) covering the period 1900-2010. This increase in frequency could be correlated with a significant departure of mean annual temperature from the 1960–1990 average, based on a dataset describing conditions in Switzerland. Paranunzio et al. 2016 systematically studied the climatic conditions and anomalies occurring before 41 rock fall events in the Italian Alps with volumes of several hundred to several million m<sup>3</sup>. They show that positive and negative temperature anomalies triggered the majority of analysed rock fall events in a complex manner, but that melting of permafrost was clearly not the only rock fall trigger.</p><p>However, there have been no studies which systematically investigate changes in the frequency of rock fall events based on complete inventories covering a large range of rock fall volumes. To fill this gap, we have generated a new database for rapid rock slope failures in the Swiss Alps covering events larger than 100’000 m<sup>3</sup> (Bühler 2019, BSc Thesis ETH 2019). This catalogue covers the period between 1700 and 2019 and includes 86 events with reliably estimated volume, date and location of occurrence, and pre-disposing factors (such as slope orientation, permafrost occurrence and geological setting). Volume-cumulative frequency plots of the events demonstrate completeness of the catalogue for all size classes, and significant changes in the ratios between large and small events through time.</p><p>An enhanced frequency of the volume class of 10<sup>5 </sup>m<sup>3</sup> (100’000-999’000 m<sup>3</sup>) is observed starting from 1940, predominantly occurring in permafrost areas and elevations ranging between 2800 and 3200 masl. This increasing frequency signal with time disappears for increasing volumes beyond a magnitude of about 400’000 m<sup>3</sup> and is clearly absent for very large rock slope failure of millions to tens of millions of m<sup>3</sup>.</p><p>The volume dependence of climate sensitivity can be physically explained, as larger volume slope failures tend to have deeper failure surfaces. Typical failure depth for multi-million m<sup>3</sup> slope failures in crystalline rocks are up to a few 100 meters, and beyond the depth of Alpine permafrost. Direct impacts of surface temperature changes on permafrost are mainly manifested through a minor thickening of the active layer, typically ranging between 1 and 10 meters, but indirect effects at the depth range of decameters (i.e. the depth of failure surfaces for events of the 10<sup>5</sup> m<sup>3</sup> class) have been assessed and demonstrated in a large number of studies.</p>

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