References of "Havenith, Hans-Balder"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailDetection of Cover Collapse Doline and Other Epikarst Features by Multiple Geophysical Techniques, Case Study of Tarimba Cave, Brazil
Hussain, Yawar ULiege; Uagoda, Rogerio; Borges, Welitom et al

in Water (2020)

Reliable characterization of the karst system is essential for risk assessment where many associated hazards (e.g., cover-collapse dolines and groundwater pollution) can a ect natural and built ... [more ▼]

Reliable characterization of the karst system is essential for risk assessment where many associated hazards (e.g., cover-collapse dolines and groundwater pollution) can a ect natural and built environments, threatening public safety. The use of multiple geophysical approaches may o er an improved way to investigate such cover-collapse sinkholes and aid in geohazard risk assessments. In this paper, covered karst, which has two types of shallow caves (vadose and fluvial) located in Tarimba (Goias, Brazil), was investigated using various geophysical methods to evaluate their e ciency in the delineation of the geometry of sediments filled sinkhole. The methods used for the investigation were Electrical Resistivity Tomography (ERT), Seismic Refraction Survey (SRS), Seismic Refraction Tomography (SRT) and the Very Low Frequency Electromagnetic (VLF-EM) method. The study developed several (2D) sections of the measured physical properties, including P-wave velocity and electrical resistivity, as well as the induced current (because of local bodies). For the analysis and processing of the data obtained from these methods, the following approaches were adopted: ERT inversion using a least-square scheme, Karous-Hjelt filter for VLF-EM data and time-distance curves and Vp cross-sections for the SRS. The refraction data analysis showed three-layered stratigraphy topsoil, claystone and carbonate bedrock, respectively. The findings obtained from ERT (three-layered stratigraphy and sediment-filled doline), as well as VLF-EM (fractured or filled caves as a positive anomaly), were found to be consistent with the actual field conditions. However, the SRS and SRT methods did not show the collapsed material and reached the limited the depth because of shorter profile lengths. The study provides a reasonable basis for the development of an integrated geophysical approach for site characterization of karst systems, particularly the perched tank and collapse doline. [less ▲]

Detailed reference viewed: 28 (1 ULiège)
Full Text
Peer Reviewed
See detailEffect of Soil Geomechanical Properties and Geo-Environmental Factors on Landslide Predisposition at Mount Oku, Cameroon
Love Djukem, Wamba Danny; Braun, Anika; Ludovic Wouatong, Armand Sylvain et al

in International Journal of Environmental Research and Public Health (2020), 17(18), 1-27

In this work, we explored a novel approach to integrate both geo-environmental and soil geomechanical parameters in a landslide susceptibility model. A total of 179 shallow to deep landslides were ... [more ▼]

In this work, we explored a novel approach to integrate both geo-environmental and soil geomechanical parameters in a landslide susceptibility model. A total of 179 shallow to deep landslides were identified using Google Earth images and field observations. Moreover, soil geomechanical properties of 11 representative soil samples were analyzed. The relationship between soil properties was evaluated using the Pearson correlation coe cient and geotechnical diagrams. Membership values were assigned to each soil property class, using the fuzzy membership method. The information value method allowed computing the weight value of geo-environmental factor classes. From the soil geomechanical membership values and the geo-environmental factor weights, three landslide predisposition models were produced, two separate models and one combined model. The results of the soil testing allowed classifying the soils in the study area as highly plastic clays, with high water content, swelling, and shrinkage potential. Some geo-environmental factor classes revealed their landslide prediction ability by displaying high weight values. While the model with only soil properties tended to underrate unstable and stable areas, the model combining soil properties and geo-environmental factors allowed a more precise identification of stability conditions. The geo-environmental factors model and the model combining geo-environmental factors and soil properties displayed predictive powers of 80 and 93%, respectively. It can be concluded that the spatial analysis of soil geomechanical properties can play a major role in the detection of landslide prone areas, which is of great interest for site selection and planning with respect to sustainable development at Mount Oku. [less ▲]

Detailed reference viewed: 20 (2 ULiège)
Full Text
Peer Reviewed
See detailAnalysis of the Influence of Structural Geology on the Massive Seismic Slope Failure Potential Supported by Numerical Modelling
Lemaire, Emilie ULiege; Mreyen, Anne-Sophie ULiege; Dufresne, Anja et al

in Geosciences (2020), 10

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 ... [more ▼]

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. [less ▲]

Detailed reference viewed: 28 (4 ULiège)
Full Text
Peer Reviewed
See detailMonitoring the Recent Activity of Landslides in the Mailuu-Suu Valley (Kyrgyzstan) Using Radar and Optical Remote Sensing Techniques
Piroton, Valentine ULiege; Schlögel, Romy; Barbier, Christian ULiege et al

in Geosciences (2020), 10(5),

Central Asian mountain regions are prone to multiple types of natural hazards, often causing damage due to the impact of mass movements. In spring 2017, Kyrgyzstan suffered significant losses from a ... [more ▼]

Central Asian mountain regions are prone to multiple types of natural hazards, often causing damage due to the impact of mass movements. In spring 2017, Kyrgyzstan suffered significant losses from a massive landslide activation event, during which also two of the largest deep-seated mass movements of the former mining area of Mailuu-Suu—the Koytash and Tektonik landslides—were reactivated. This study consists of the use of optical and radar satellite data to highlight deformation zones and identify displacements prior to the collapse of Koytash and to the more superficial deformation on Tektonik. Especially for the first one, the comparison of Digital Elevation Models of 2011 and 2017 (respectively, satellite and unmanned aerial vehicle (UAV) imagery-based) highlights areas of depletion and accumulation, in the scarp and near the toe, respectively. The Differential Synthetic Aperture Radar Interferometry analysis identified slow displacements during the months preceding the reactivation in April 2017, indicating the long-term sliding activity of Koytash and Tektonik. This was confirmed by the computation of deformation time series, showing a positive velocity anomaly on the upper part of both landslides. Furthermore, the analysis of the Normalized Difference Vegetation Index revealed land cover changes associated with the sliding process between June 2016 and October 2017. In addition, in situ data from a local meteorological station highlighted the important contribution of precipitation as a trigger of the collapse. The multidirectional approach used in this study demonstrated the efficiency of applying multiple remote sensing techniques, combined with a meteorological analysis, to identify triggering factors and monitor the activity of landslides. [less ▲]

Detailed reference viewed: 31 (4 ULiège)
Full Text
Peer Reviewed
See detailDisaster Risk in Central Asia: Socio-Economic Vulnerability Context and Pilot-Study of Multi-Risk Assessment in A Remote Mountain Area of the Kyrgyz Republic
Umaraliev, Ruslan; Moura, Rui; Havenith, Hans-Balder ULiege et al

in European Journal of Engineering Research and Science (2020), 5

Abstract—The Kyrgyz Republic, as well as other countries of Central Asia, is highly exposed to natural-environmental hazards, which continues undermining efforts to achieve sustainable development ... [more ▼]

Abstract—The Kyrgyz Republic, as well as other countries of Central Asia, is highly exposed to natural-environmental hazards, which continues undermining efforts to achieve sustainable development. National disaster risk assessment procedures in Central Asian countries are mainly based on the evaluation of hazards without a detailed analysis of vulnerability and resilience. Additionally, the available practices of hazard assessments are mostly based on a zone-byzone approach, which would make it difficult to develop a comparative assessment of facilities located in the same hazard zone. This situation hampers the efforts of the local governments to effectively plan and implement disaster risk reduction (DRR) actions when they cannot differentiate the individual facilities according to the risk level in order to focus the existing capacity (which is usually very limited) on increasing the resilience and reducing the vulnerability of the facilities with the highest risk. For improvement of DRR practices, the quantitative comprehensive approach of risk analysis applied in this study is used for risk assessment of educational institutions in one of the most seismically active and most disaster-prone mountain regions of Central Asia - the Alay valley, a wide intermontane valley situated in between the two biggest mountain systems in Asia: Tian Shan and Pamir. The developed multidisciplinary study suggests that the quantitative multi-risk assessment approach - can play a crucial role in understanding risks and can significantly improve the quality of disaster risk reduction planning. [less ▲]

Detailed reference viewed: 28 (2 ULiège)
Full Text
Peer Reviewed
See detailThe added value of a regional landslide susceptibility assessment: The western branch of the East African Rift
Depicker, A.; Jacobs, L.; Delvaux, David et al

in Geomorphology (2020), 353

Predicting landslide occurrence is of key importance for understanding the geomorphological development of mountain environments as well as to assess the potential risk posed by landsliding to human ... [more ▼]

Predicting landslide occurrence is of key importance for understanding the geomorphological development of mountain environments as well as to assess the potential risk posed by landsliding to human societies in such environments. Global landslide susceptibility models use a generic model formulation to predict landslide susceptibility anywhere on the planet from openly available data. Regional models, on the contrary, use local information on landslide occurrence to constrain model parameters and may also benefit from better spatial information with respect to controlling factors. This study aims to investigate the added value of the construction of regional landslide susceptibility models (versus global and continental models) in the western branch of the East African Rift, a data-scarce landslide-prone tropical environment. First, a comprehensive landslide database containing 6446 instances was compiled for the study area using Google Earth imagery. Second, three regional data-driven landslide susceptibility models were developed. Third, the efforts to construct these regional models were quantified by analysing how their quality is impacted by (1) the use of more accurate, regional peak ground acceleration and geology data, and (2) an increasing inventory size. Fourth, regional and global/continental models were compared in terms of predictive power and geomorphological plausibility. We observe that global/continental landslide susceptibility models are capable of identifying landslide-prone areas, but lack prediction power and geomorphological plausibility when compared to our regional models. Importantly, this difference in quality is not driven by the use of more accurate and detailed geology and peak ground acceleration data, but rather by the use of a detailed regional landslide inventory to calibrate the models. We also show that the model quality only increases marginally beyond a certain inventory size. We conclude that the regional landslide susceptibility assessment does provide an added value compared to existing global models in terms of geomorphological plausibility and model performance, whereby the largest gain is to be found in the construction of a regional landslide inventory, rather than the investment in more detailed covariates or the application of more complex modelling techniques. The latter suggests that the role of controlling variables depends, to some extent, on the regional context: making adequate susceptibility predictions proves difficult when local conditions are not accounted for by means of a regional inventory. © 2019 Elsevier B.V. [less ▲]

Detailed reference viewed: 29 (1 ULiège)
Full Text
Peer Reviewed
See detailTopographic and near-surface stratigraphic amplification of the seismic response of a mountain slope revealed by field monitoring and numerical simulations
Luo, Y.; Fan, X.; Huang, R. et al

in Engineering Geology (2020), 271

The evaluation of seismic site amplification and its relationship with geological structures play a vital role in earthquake engineering and hazard assessment. This study presents an analysis of ... [more ▼]

The evaluation of seismic site amplification and its relationship with geological structures play a vital role in earthquake engineering and hazard assessment. This study presents an analysis of topographic and geologic site amplification effects observed in the Qiaozhuang region, Sichuan Province, China. Seismic recordings at several monitoring stations installed on two slopes located at a distance of about 1 km in the study area after the 2008 Wenchuan earthquake provide evidence of strong and variable amplifications. To assess the combined effect of topographic and geological controls in slope response to seismic motions, we built 2D and 3D dynamic numerical models using monitoring data as inputs. Four layers with different P-wave velocities, based on geophysical survey in the study area, are considered in the numerical models. Models that only consider topography give an amplification factor of <3, which is much lower than the amplification factor of 5–6 from the monitoring data, while those models that considered both the topographic variation and four layers agree well with the monitoring data. The 3D modeling results show that the subsurface amplification factor is less than that on the slope surface even at the same elevation. This is also consistent with the monitoring data and further indicates that the combined topographic and geological amplification effect on the slope surface is more significant than the sole geological amplification effect inside the slope. Our numerical simulation results suggest that it is important to consider the combined topographic and geological amplification effects in the hazard assessment of seismically induced slope failures. © 2020 Elsevier B.V. [less ▲]

Detailed reference viewed: 31 (1 ULiège)
Full Text
Peer Reviewed
See detailA new landslide inventory for the armenian lesser caucasus: Slope failure morphologies and seismotectonic influences on large landslides
Matossian, A. O.; Baghdasaryan, H.; Avagyan, A. et al

in Geosciences (2020), 10(3),

Landslide hazard analyses in Armenia require consideration of the seismotectonic context of the Lesser Caucasus. As it is located near the center of the Arab-Eurasian collision, the Lesser Caucasus is ... [more ▼]

Landslide hazard analyses in Armenia require consideration of the seismotectonic context of the Lesser Caucasus. As it is located near the center of the Arab-Eurasian collision, the Lesser Caucasus is characterized by its complex geology, dense fault network and mountainous relief; it is marked by recent volcanic and seismic activity largely influencing slope stability at different scales. We therefore sought to identify all major landslides in the Armenian Lesser Caucasus and to understand the environmental factors contributing to regional landslide susceptibility. We performed spatial and size-frequency analyses using two landslide catalogues as inputs: “Georisk”, provided by the Georisk Scientific Research Company, and “Matossian”, herein. Our spatial analyses show that landslide susceptibility depends on many factors according to the area considered: near faults, a tectonic influence on slope stability is clearly observable, whereas high concentrations of landslides in northern mountain regions, marked by a wetter climate and far from known active faults, show that climatic factors also strongly contribute to slope-failure potential. The influence of volcanoes and volcanic deposits on the development of mass movements is unclear and requires further analysis. The aforementioned inventories do not include any records of volcanic flank collapses, although we expect at least one case in the eastern Lesser Caucasus. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. [less ▲]

Detailed reference viewed: 25 (1 ULiège)
Full Text
Peer Reviewed
See detailSeismotectonic activity in East Belgium: relevance of a major scarp and two associated landslides in the region of Malmedy
Mreyen, Anne-Sophie ULiege; Demoulin, Alain ULiege; Havenith, Hans-Balder ULiege

in Geologica Belgica (2018), 21(3-4), 101-110

Geomorphological markers such as scarps, river diversions and slope failures can be used as proxy indicators for the seismotectonic activity of a region. This study concentrates on the Malmedy-Bévercé ... [more ▼]

Geomorphological markers such as scarps, river diversions and slope failures can be used as proxy indicators for the seismotectonic activity of a region. This study concentrates on the Malmedy-Bévercé area, E-Belgium, where formerly unknown geomorphological features have been recently discovered in the frame of a new regional geological mapping campaign. The area is characterised by gentle to locally very steep slopes along the Warche valley crossing the Stavelot Massif and the Malmedy Graben. Coupled with a LiDAR-DEM and UAV imagery analysis, field mapping has revealed a steep scarp extending near two landslides on the southern hillslopes of the Warche valley at Bévercé. These slope failures developed in the Permian conglomerates of the Malmedy Formation (also known as the Poudingue de Malmedy), which represent the infill of the Malmedy Graben. Roughly perpendicular to the graben axis, the scarp has a N330°E orientation similar to that of the seismotectonically active Hockai Fault Zone that crosses the Malmedy region in this area. In this paper, we present the geological and geomorphological context of the Bévercé scarp and of the largest landslide. Furthermore, we demonstrate the results of a geophysical reconnaissance survey of the structures (seismic refraction and electrical resistivity profiling). The geophysical results highlight a vertical displacement of the seismic layers and laterally changing electrical properties across the scarp, with very low resistivity values in its middle part. A low resistivity zone in the subsurface can also be found within the larger landslide, right in the prolongation of the scarp. All these observations hint at the presence of a major, probably seismically active, fault belonging to the eastern border of the Hockai Fault Zone. [less ▲]

Detailed reference viewed: 97 (14 ULiège)
Full Text
Peer Reviewed
See detailFormation, breaching and flood consequences of a landslide dam near Bujumbura, Burundi
Nibigira, Léonidas ULiege; Havenith, Hans-Balder ULiege; Archambeau, Pierre ULiege et al

in Natural Hazards and Earth System Sciences (2018), 18

This paper investigates the possible formation of a landslide dam on the Kanyosha River near Bujumbura, the capital of Burundi, as well as the interplay between the breaching of this landslide dam and the ... [more ▼]

This paper investigates the possible formation of a landslide dam on the Kanyosha River near Bujumbura, the capital of Burundi, as well as the interplay between the breaching of this landslide dam and the flooding along the river. We present an end-to-end analysis, ranging from the origin of the landslide up to the computation of flood waves induced by the dam breaching. The study includes three main steps. First, the mass movement site was investigated with various geophysical methods that allowed us to build a general 3D model and detailed 2D sections of the landslide. Second, this model was used for dynamic landslide process modelling with the Universal Distinct Element Code. The results showed that a fifteen-meter-high landslide dam may form on the river. Finally, a 2D hydraulic model was setup to find out the consequences of the breaching of the landslide dam on flooding along the river, especially in an urban area located downstream. Based on 2D maps of maximum water depth, flow velocity and wave propagation time, the results highlight that neglecting the influence of such landslide dams leads to substantial underestimation of flood intensity in the downstream area. [less ▲]

Detailed reference viewed: 121 (18 ULiège)
Full Text
Peer Reviewed
See detailSite Effect Assessment of the Gros-Morne Hill Area in Port-au-Prince, Haiti, Part A: Geophysical-Seismological Survey Results
Ulysse, Sophia Marie Johanne ULiege; Boisson, Dominique; Preptit, Claude et al

in Geosciences (2018), 8

After the M = 7.0 Haiti earthquake in 2010, many teams completed seismic risk studies in Port-au-Prince to better understand why this not extraordinarily strong event had induced one of the most severe ... [more ▼]

After the M = 7.0 Haiti earthquake in 2010, many teams completed seismic risk studies in Port-au-Prince to better understand why this not extraordinarily strong event had induced one of the most severe earthquake disasters in history (at least in the Western World). Most highlighted the low construction quality as the main cause for the disaster, but some also pointed to possible soil and topographic amplification effects, especially in the lower and central parts of Port-au-Prince (e.g., close to the harbor). However, very detailed local studies of such site effects have not been completed yet. A Belgian-Haitian collaboration project was established in order to develop a detailed local seismic hazard study for Gros-Morne hill located in the district of P étion-Ville, southeast of Port-au-Prince. In order to have a better understanding of the amplification on the Gros-Morne hill, in the southeastern part of Port-au-Prince, site effects were investigated by using near surface geophysical methods. The horizontal to vertical spectral ratio technique was applied to ambient vibrations and earthquake data, and multichannel analysis of surface waves and P-wave refraction tomography calculation were applied to seismic data. Standard spectral ratios were computed for the S-wave windows of the earthquake data recorded by a small temporary seismic network. Electrical resistivity tomography profiles were also performed in order to image the structure of the subsurface and detect the presence of water, if any. The spectral ratio results generally show low to medium (1.5–6) resonance amplitudes at one or several different resonance frequencies (for the same site), between 0.5 and 25 Hz. At most of the investigated sites, the fundamental resonance frequency varies between 7 and 10 Hz. By using the multichannel surface wave analyses of the seismic data, we were able to determine shear wave velocities ranging between 200 and 850 m/s, up to a depth of about 15–20 m. From the refraction analysis, we were able to delineate P-waves velocities of 500 to 1500–2000 m/s at the studied sites. The outputs were locally compared with the resistivity data from the electrical profiles. Thus, the overall data indicate a moderate site effect at Gros-Morne hill, with a great variability in site amplification distribution. Initial estimates of local site effects were made on the basis of those outputs and the earthquake recordings. Our results are finally discussed with respect to outputs and interpretations that had been published earlier for the same site. Those results only partly confirm the strong seismic amplification effects highlighted by previous papers for this hill site, which had been explained by the effects of the local topographic and soil characteristics. [less ▲]

Detailed reference viewed: 50 (8 ULiège)
Full Text
Peer Reviewed
See detailWhat we have learned from the 2008 Wenchuan Earthquake and its aftermath: A decade of research and challenges
Fan, X.; Juang, C. H.; Wasowski, J. et al

in Engineering Geology (2018), 241

The 2008 Mw 7.9 Wenchuan Earthquake (Sichuan, China) was possibly the largest and most destructive recent earthquake as far as the geo-hazards are concerned. Of the nearly 200,000 landslides triggered ... [more ▼]

The 2008 Mw 7.9 Wenchuan Earthquake (Sichuan, China) was possibly the largest and most destructive recent earthquake as far as the geo-hazards are concerned. Of the nearly 200,000 landslides triggered originally, many remobilized within a few years after the initial event by rainfall, which often caused catastrophic debris flows. The cascades of geo-hazards related to the Wenchuan Earthquake motivated research worldwide to investigate the triggering and mechanisms of co-seismic landslides, their rainfall-induced remobilization, the generation of debris flows, the evolution of their controlling factors, and the long-term role of earthquakes in shaping the topography. On the eve of the 10th anniversary of the 2008 Wenchuan Earthquake, we present a short review of the recent advances in these topics, discuss the challenges faced in the earthquake-related geo-hazards mitigation practice, and suggest priorities and guidelines for future research. © 2018 Elsevier B.V. [less ▲]

Detailed reference viewed: 33 (1 ULiège)
Full Text
Peer Reviewed
See detailAnalyzing successive landslide dam formation by different triggering mechanisms: The case of the Tangjiawan landslide, Sichuan, China
Fan, X.; Zhan, W.; Dong, X. et al

in Engineering Geology (2018), 243

The catastrophic Tangjiawan landslide, triggered by the 2008 Wenchuan earthquake, blocked the Duba River, impounding one of the most dangerous coseismic barrier lakes in Beichuan, China. The lake was ... [more ▼]

The catastrophic Tangjiawan landslide, triggered by the 2008 Wenchuan earthquake, blocked the Duba River, impounding one of the most dangerous coseismic barrier lakes in Beichuan, China. The lake was drained by an artificial spillway within one month after the earthquake to minimize the potential dam-breach flooding risk. However, on September 5, 2016, this landslide was reactivated and dammed the river again, creating a 20-m high dam at the same location and resulting in the formation of a barrier lake with a volume of 0.6 million m3. The day after the event we carried out a field investigation of the landslide and obtained a high-resolution image and DEM using UAV. The satellite images from 2005, 2008, 2010 and 2015 were also collected to analyze the evolution of the landslide. Together with multi-temporal DEMs, the geometry and volumes of the displaced mass and the landslide dams and barrier lakes were calculated using image interpretation and 3D spatial analysis with GIS. This landslide is of great scientific interest, as it presents a good example of multiple reactivation of a pre-historical giant landslide under different triggering conditions: a reactivation of an older landslide during the Wenchuan earthquake, and a second reactivation during a rainfall event several years later. Meanwhile from the hazard assessment and prevention perspective, it is also representative as it dammed the river twice in 2008 and 2016, posing threats to both upstream and downstream areas. We infer that the successive landslides in this region could be caused by the strong tectonic activities: including earthquakes and high average uplifting rate. The results of landslide volume analysis using multi-temporal DEMs, contribute to the landslide mechanism analysis, and suggest that the landslide volume estimation is effected by the landslide type, landslide rupture surface location, and resolution of DEM. We also compare the performance of different empirical models of landslide stability and dam-breach flood parameters and discuss their application during the quick assessment of the potential hazard of the landslide dams. Generally, the successive landslide dams at the Tangjiawan site are caused by the successive landslide reactivations on an anti-dip slope controlled by strong tectonic activity and river erosion, involve with a mass of loose materials of previous landslide deposition, and possess high flood risk to the downstream area. The experience gained in this work can be used to assist the hazard assessment and the planning of the emergency measures for similar landslide dams in the future. © 2018 Elsevier B.V. [less ▲]

Detailed reference viewed: 31 (1 ULiège)
Full Text
Peer Reviewed
See detailSite effect assessment of the gros-morne hill area in port-au-prince, haiti, part B: Mapping and modelling results
Ulysse, Sophia Marie Johanne ULiege; Boisson, D.; Prépetit, C. et al

in Geosciences (2018), 8(7),

This paper presents the general results in terms of maps, as well as geological and numerical models of a site effect study, that aimed at a better understanding of the ground motion amplification on the ... [more ▼]

This paper presents the general results in terms of maps, as well as geological and numerical models of a site effect study, that aimed at a better understanding of the ground motion amplification on the Gros-Morne hill, in the southeastern part of Port-au-Prince, Haiti, which might have influenced the 2010 event damage pattern in that area. These maps and models are based on multiple geophysical–seismological survey outputs that are presented, in detail, in Part A of this publication. Those outputs include electrical resistivity tomography sections, P-wave velocity profiles, S-wave logs, estimates of the fundamental resonance frequency for many locations, as well as earthquake recordings at three sites and associated site amplification assessment for the top of the hill. Related results are discussed in Part A with respect to outputs and interpretations that had been published earlier by other research teams for the same site. Our results only partly confirm the strong seismic amplification effects highlighted by some of the previous studies for this hill site, which had been attributed to the influence of local topographic and soil characteristics on seismic ground motion. Here, we focus on the imaging of different site effect components over the entire survey area; we present maps of shear wave velocity variations, of changing fundamental resonance frequencies, and of related estimates of soft soil/rock thickness, of peak spectral amplitudes, and of ambient ground motion polarization. Results have also been compiled within a 3D surface–subsurface model of the hill, which helps visualize the geological characteristics of the area, which are relevant for site effect analyses. From the 3D geomodel, we extracted one 2D geological section along the short-axis of the hill, crossing it near the location of Hotel Montana on top of the hill, which had been destroyed during the earthquake, and has now been rebuilt. This cross-section was used for dynamic numerical modelling of seismic ground motion, and for related site amplification calculation. The numerical results are compared with the site amplification characteristics that had been estimated from the ambient vibration measurements and the earthquake recordings. © 2018 by the authors. Licensee MDPI, Basel, Switzerland. [less ▲]

Detailed reference viewed: 37 (2 ULiège)
Full Text
Peer Reviewed
See detailDistinctive controls on the distribution of river-damming and non-damming landslides induced by the 2008 Wenchuan earthquake
Tang, R.; Fan, X.; Scaringi, G. et al

in Bulletin of Engineering Geology and the Environment (2018)

The 2008 Wenchuan earthquake (China, Mw 7.9) highlighted the importance of assessing and mitigating the hazards from co-seismic landslides and landslide dams. The seismic shaking triggered hundreds of ... [more ▼]

The 2008 Wenchuan earthquake (China, Mw 7.9) highlighted the importance of assessing and mitigating the hazards from co-seismic landslides and landslide dams. The seismic shaking triggered hundreds of thousands of landslides, about 800 of which dammed the course of rivers. To understand whether distinctive factors concurred with the river-damming events, we analyzed the spatial patterns of the river-damming landslides and the non-damming landslides separately, with reference to a number of possible controlling factors. Then, we quantified the significance of these factors using the weight of evidence method, and we used the results to perform a susceptibility assessment in a portion of the earthquake-affected region to verify the effectiveness of the method. We find that the distance to the fault surface rupture, peak ground acceleration (PGA) and lithology play a controlling role for co-seismic landslides of any type. The occurrence of river-damming landslides, rather than by a specific lithology or topography, is more related to hydrological factors, while topographic controls (slope, internal relief and terrain roughness) are more significant for the non-damming landslides. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature. [less ▲]

Detailed reference viewed: 31 (1 ULiège)
Full Text
Peer Reviewed
See detailIntegrated Geophysical-Geological 3D Model of the Right-Bank Slope Downstream from the Rogun Dam Construction Site, Tajikistan
Havenith, Hans-Balder ULiege; Torgoev, I.; Ischuk, A.

in International Journal of Geophysics (2018), 2018

In summer of 2015 we had completed a geophysical survey complemented by borehole drilling near the right-bank slope of the Rogun Dam construction site, Tajikistan. These data were first processed and then ... [more ▼]

In summer of 2015 we had completed a geophysical survey complemented by borehole drilling near the right-bank slope of the Rogun Dam construction site, Tajikistan. These data were first processed and then compiled within a 3D geomodel. The present paper describes the geophysical results and the 3D geomodel generated for an ancient mass movement located immediately downstream from the construction site. The geophysical survey included electrical and seismic profiles and ambient vibration measurements as well as earthquake recordings. The electrical and seismic data were processed as tomographic sections, the ambient vibrations as horizontal-to-vertical spectral H/V ratios, and the earthquake data mainly in terms of standard spectral ratios. By estimating the average shear wave velocities of the subsurface, we computed the local soft layer thickness from the resonance frequencies revealed by the H/V ratios. Three seismic stations had been installed for ten days along a profile crossing the intermediate plateau. Standard spectral ratios inferred from ten processed earthquake measurements confirmed the presence of a thick soft material layer on the plateau made of weathered rocks, colluvium, and terrace deposits, which produce a medium-level amplification at about 2 Hz. The 3D geomodel was first built on the basis of new topographic data, satellite imagery, and a geological map with two sections. Then, the various electrical resistivity and seismic refraction tomographies were inserted in the geomodel. The soft layer thickness information and borehole data were represented in terms of logs in the model. The site is crossed by the Ionakhsh Fault that could be modeled on the basis of the geological inputs and of a lateral resistivity gradient found on one electrical profile along the steep lower slope. The integrated interpretation of all results reveals that probably only a relatively small part of the ancient giant mass movement is really exposed to slope instability phenomena. © 2018 Hans-Balder Havenith et al. [less ▲]

Detailed reference viewed: 29 (2 ULiège)
See detailModelle zur Untersuchung von Massenbewegungen und Hangstabilität in seismischen Regionen
Mreyen, Anne-Sophie ULiege; Anja, Dufresne; Havenith, Hans-Balder ULiege

in Fachsektionstage Geotechnik - Interdisziplinäres Forum (2017, September)

Zwei von Erdrutschen betroffene Regionen in NW- und Mitteleuropa werden mittels Hangstabilitätsanalysen in Form von 3D-Geo-Modellen und numerischer 2D-Modellierung untersucht: (1) die Hockai-Störungszone ... [more ▼]

Zwei von Erdrutschen betroffene Regionen in NW- und Mitteleuropa werden mittels Hangstabilitätsanalysen in Form von 3D-Geo-Modellen und numerischer 2D-Modellierung untersucht: (1) die Hockai-Störungszone (HFZ – Hockai Fault Zone) in Ostbelgien und (2) die seismische Region Vrancea in den rumänischen Karpaten. Die Untersuchungsgebiete unterscheiden sich hinsichtlich ihrer klimatischen und seismo-tektonischen Bedingungen, sind jedoch beide von tiefsitzenden Hangbewegungen entlang aktiver bzw. inaktiver Störungszonen betroffen. Obwohl es zurzeit keinerlei eindeutige Belege massiver co-seismischer Erdrutsche in NW Europa gibt, ist die seismisch aktive HFZ in Belgien (bekannt durch das M~6-6.3 Verviers Ereignis in 1692) durch größere Massenbewegungen mit wahrscheinlichem seismischen Ursprung gekennzeichnet. Die Region Vrancea in Rumänien dagegen ist von kleineren (< 1 Mio. m³) bekannten seismischen Massenbewegungen geprägt (ausgelöst durch Erdbeben in 1940 und 1977). In solchen Regionen müssen dynamische Stabilitätsanalysen potentielles Bodenversagen durch Erdbeben berücksichtigen. Um die Massenbewegungen beider Regionen aufzuschließen, wurden verschiedene Methoden angewandt. Zu den Erkundungsmethoden zählen geotechnische, geologische und geomorphologische Untersuchungen, wie auch geophysikalische Methoden: ERT (electrical resistivity tomography), mikroseismische Bodenunruhe-Messungen (H/V-Methode), sowie SRT (seismic refraction tomography) samt Analyse seismischer Oberflächenwellen. Insbesondere die H/V-Methode ist eine zunehmend gebräuchliche Methode zur Erkundung von Hangrutschungen (1D-Abschätzung von Lockersedimentschichten, d.h. in diesem Fall von gestörten Bodenschichten). Geomechanische Eigenschaften des Hangmaterials wurden mithilfe von kleinen geotechnischen Studien (Erkundungsbohrungen, Schmidt Hammer, Strukturanalysen) und seismischen Parametern ermittelt. 3D-Geo-Modelle ermöglichen die Integration der gemessenen Daten durch Datenfusion und geostatistische Techniken. Dabei wird die Modelloberfläche anhand hochauflösender Fernerkundungsdaten (1 m LiDAR – Light Detection and Ranging) abgebildet, der Untergrund des Untersuchungsgebiets hingegen durch die Modellierung geologischer Trennflächen und Volumina. Die Geo-Modelle dienen als Basis zur Übertragung der ermittelten Daten in 2D numerische Modelle. Eine dynamische back-analysis der Untersuchungsgebiete ermöglicht die numerische Berechnung seismischer Auswirkungen auf die rutschungsanfälligen Hänge. [less ▲]

Detailed reference viewed: 78 (3 ULiège)
Full Text
Peer Reviewed
See detailGeotechnical Assessment of Potential Mass Movement Occurrence in a Zone at Risk Around Yaoundé-Cameroon
Mukenga, Williams ULiege; Havenith, Hans-Balder ULiege; Medjo Eko, Robert et al

in Mikos, Matjaz; Tiwari, B; Yin, Y (Eds.) et al Advancing Culture of Living with Landslise: 4WLF, Ljubljana 29 mai au 2 juin 2017 (2017, June 11)

Mass movements represent a major threat to human life, properties and infrastructures in most densely populated and hilly towns in humid tropical areas. The present work is focused on the evaluation of ... [more ▼]

Mass movements represent a major threat to human life, properties and infrastructures in most densely populated and hilly towns in humid tropical areas. The present work is focused on the evaluation of the safety factor of natural slopes of mount Eloumden, located at the West-South-West of Yaoundé, and on a contribution to address various problems related to the uncontrolled occupation of natural areas and the consequent potential mass movement occurrence. This natural slope stability study was carried out on the basis of field and laboratory tests: physical identification and geomechanical characterization of constituent materials from natural risk zone. The results obtained show that: the basement is made up of gneiss and the soil is ferrallitic; the constituent materials are silty-sand of the class A-6 (13) and A-6 (14), plastic, averagely water saturated, over consolidated and highly compressible. Their compaction can be tolerated when their preconsolidation stress is greater than their final effective stress; the short term factors of safety of these natural slopes, calculated on Excel, have values between 1.579 and 1.296 according to Fellenius for EL1 and EL2; 1.714 and 1.392 according to Bishop simplified. This infers that the slope EL1 is stable (Fs> 1.4) while the slope EL2 is potentially unstable (Fs<1.4).Depending on simulations, the factor of safety decreases progressively in the presence of groundwater flow; with the reduction of the cohesion and with an increase of the density of the wet soil. [less ▲]

Detailed reference viewed: 27 (4 ULiège)
Peer Reviewed
See detailIntegrated Geological-Geophysical Models of Unstable Slopes in Seismic Areas
Mreyen, Anne-Sophie ULiege; Micu, Mihai; Onaca, Alexandru et al

in Mikos, Matjaz (Ed.) Advancing Culture of Living with Landslides (2017, May)

We will present a series of new integrated 3D models of landslide sites that were investigated in distinctive seismotectonic and climatic contexts: (1) along the Hockai Fault Zone in Belgium and (2) in ... [more ▼]

We will present a series of new integrated 3D models of landslide sites that were investigated in distinctive seismotectonic and climatic contexts: (1) along the Hockai Fault Zone in Belgium and (2) in the seismic region of Vrancea, Romania. Both sites are deep-seated failures located in more or less seismically active areas. In such areas, slope stability analyses have to take into account the possible contributions to ground failure. Our investigation methods had to be adapted to capture the deep structure as well as the physico-mechanical characteristics that influence the dynamic behaviour of the landslide body. Field surveys included electrical resistivity tomography profiles, seismic refraction profiles (analysed in terms of both seismic P-wave tomography and surface waves), ambient noise measurements to determine the soil resonance frequencies through H/V analysis, complemented by geological and geomorphic mapping. The H/V method, in particular, is more and more used for landslide investigations or sites marked by topographic relief (in addition to the more classical applications on flat sites). Results of data interpretation were compiled in 3D geological-geophysical models supported by high resolution remote sensing data of the ground surface. Data and results were not only analysed in parallel or successively; to ensure full integration of all inputs-outputs, some data fusion and geostatistical techniques were applied to establish closer links between them. Inside the 3D models, material boundaries were defined in terms of surfaces and volumes. Those were implemented in 2D and 3D numerical dynamic models (presented in a companion paper). [less ▲]

Detailed reference viewed: 136 (31 ULiège)
Peer Reviewed
See detailAnalysis of Migration in a Multi-Risk Context: Case of Bujumbura/Burundi
Nibigira, Léonidas ULiege; Ozer, Pierre ULiege; Havenith, Hans-Balder ULiege

in MAIER, ROBIN; REVELL, MARK (Eds.) THE AMERICAN ASSOCIATION OF GEOGRAPHERS, 2017 Annual Meeting, April 5 - 9, 2017 Boston, Massachusetts / PROGRAM (2017, April 08)

Human mobility affects land use and human density distribution. Unfortunately, this rarely takes into account the real and potential changes induced by hazards on the natural systems. Thus, migration and ... [more ▼]

Human mobility affects land use and human density distribution. Unfortunately, this rarely takes into account the real and potential changes induced by hazards on the natural systems. Thus, migration and natural hazards should be constantly analyzed through cross-sectional and global studies to reduce disastrous consequences resulting from their mutual interactions. In a multi-risk and demographic sprawl context, the study focused on the cross-analysis of human density and natural hazards in Bujumbura. The results show that migration of people should ideally be guided by knowledge of the area's sensitivity to natural hazards, taking into account other parameters such as hazards susceptibility maps and production opportunities. While the migration of people toward overcrowded centers constitutes a big challenge, it is an important asset when it concerns areas in need of manpower. It also allows the balance in relieving saturated areas, reducing human pressure on the environment. Therefore, there is a need that policymakers comply with those aspects, finding the right balance for a better situation. [less ▲]

Detailed reference viewed: 95 (20 ULiège)