An essential component of a quantitative landslide hazard assessment is establishing the extent of the endangered area. This task requires accurate prediction of the run-out behaviour of a landslide, which includes the estimation of the... more
An essential component of a quantitative landslide hazard assessment is establishing the extent of the endangered area. This task requires accurate prediction of the run-out behaviour of a landslide, which includes the estimation of the run-out distance, run-out width, velocities, pressures, and depth of the moving mass and the final configuration of the deposits. One approach to run-out modelling is to reproduce accurately the dynamics of the propagation processes. A number of dynamic numerical models are able to compute the movement of the flow over irregular topographic terrains (3-D) controlled by a complex interaction between mechanical properties that may vary in space and time. Given the number of unknown parameters and the fact that most of the rheological parameters cannot be measured in the laboratory or field, the parametrization of run-out models is very difficult in practice. For this reason, the application of run-out models is mostly used for back-analysis of past eve...
As one of 13 new `Centres of Excellence' awarded by the Norwegian Research Council with a 10-year funding schedule, the International Centre for Geohazards (ICG) was established at the Norwegian Geotechnical Institute (NGI), in... more
As one of 13 new `Centres of Excellence' awarded by the Norwegian Research Council with a 10-year funding schedule, the International Centre for Geohazards (ICG) was established at the Norwegian Geotechnical Institute (NGI), in January 2003. The Centre is formed through a co-operation between several institutions, which in addition to NGI are the Gelogical Survey of Norway (NGU), Norwegian Seismic Array (NORSAR), University of Oslo (UiO) and the Norwegian University for Science and Technology (NTNU). The Centre is located in the NGI building in Oslo, Norway. Funding is for 10 years, and the centre is staffed by researchers from the partner institutions, visiting scientists, post-doctoral fellows and Ph.D. students. With the ultimate goal of geohazard mitigation and preventing the loss of lives and damage to infrastructure and environment, key research topics of the Centre are: Unsaturated soils and mechanisms for precipitation-induced slides in steep slopes; Risk and vulnerabili...
The December 26 2004 tsunami event devastated large areas along the coastlines of Indonesia, Thailand, Myanmar, Sri Lanka and India, and even some parts of the east African coastline. It is a great challenge to the authorities in the... more
The December 26 2004 tsunami event devastated large areas along the coastlines of Indonesia, Thailand, Myanmar, Sri Lanka and India, and even some parts of the east African coastline. It is a great challenge to the authorities in the countries affected by the tsunami to deal with the future risk of tsunami events and how to rehabilitate the devastated areas under consideration of that risk. On initiative from the Norwegian Geotechnical Institute (NGI), a project has been initiated to help develop a rehabilitation strategy in Thailand, but it is also intended as serve as an example project for other countries in the region. The project is undertaken for the Department of Mineral Resources (DMR) under the Ministry of Natural Resources and the Environment in Thailand, and is undertaken by NGI in cooperation with CCOP. The project is fully financed by the Royal Norwegian Ministry of Foreign Affairs. The paper describes the various components of the project, including: 1. Identification ...
Landslides represent a major threat to human life, property and constructed facilities, infrastructure and natural environment in most mountainous and hilly regions of the world. As a consequence of climatic changes and potential global... more
Landslides represent a major threat to human life, property and constructed facilities, infrastructure and natural environment in most mountainous and hilly regions of the world. As a consequence of climatic changes and potential global warming, an increase of landslide activity is expected in some parts of the world in the future. This will be due to increased extreme rainfall events, changes of hydrological cycles, meteorological events followed by sea storms causing coastal erosion and melting of snow and of frozen soils in the high mountains. During the past century, Europe experienced many fatalities and significant economic losses due to landslides. Since in many parts of Europe landslides are the most serious natural hazard, several recent European research projects are looking into the effects of climate change on the risk associated with landslides. Examples are the recently initiated SafeLand project, which looks into this problem across the continent, and GeoExtreme, whic...
Structural reliability theory has a significant impact on the development of modern design codes. Much of its success could be attributed to the advent of the first-order reliability method (FORM). This paper presents a state-of-the art... more
Structural reliability theory has a significant impact on the development of modern design codes. Much of its success could be attributed to the advent of the first-order reliability method (FORM). This paper presents a state-of-the art review on modeling dependent non-Gaussian random vectors for FORM. FORM solution in standard space using Cholesky factorization is recommended to ensure that variables are
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The following new function is proposed for estimating thresholds for rainfall-triggered landslides: I = alpha1Analpha2Dbeta, where I is rainfall intensity in mm/h, D is rainfall duration in h, An is the n-hours or n-days antecedent... more
The following new function is proposed for estimating thresholds for rainfall-triggered landslides: I = alpha1Analpha2Dbeta, where I is rainfall intensity in mm/h, D is rainfall duration in h, An is the n-hours or n-days antecedent precipitation, and alpha1, alpha2, beta and n are threshold parameters. A threshold model that combines two functions with different durations of antecedent precipitation is also introduced. A storm observation exceeds the threshold when the storm parameters are located at or above the two functions simultaneously. A novel optimisation procedure for estimating the threshold parameters is proposed using Receiver Operating Characteristics (ROC) analysis. The new threshold function and optimisation procedure are applied for estimating thresholds for triggering of debris flows in the Western Metropolitan Area of San Salvador (AMSS), El Salvador, where up to 500 casualties were produced by a single event. The resulting thresholds are I = 2322 A7d-1D-0.43 and I...
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Geohazards such as earthquakes or landslides represent a major risk to structures. In this contribution risk acceptance criteria for structures subjected to geohazards are reviewed. Especially the implementation of human safety and cost... more
Geohazards such as earthquakes or landslides represent a major risk to structures. In this contribution risk acceptance criteria for structures subjected to geohazards are reviewed. Especially the implementation of human safety and cost benefit considerations are discussed. Current trends in the definition of target safety criteria for structures subjected to earthquakes and landslides are presented and conclusions regarding codified criteria
The research done previously in the SafeLand project (www.safeland-fp7.eu) identified the hotspots of landslide hazard and risk in Europe using three different models. All models were, however, based on the same input data. The analyses... more
The research done previously in the SafeLand project (www.safeland-fp7.eu) identified the hotspots of landslide hazard and risk in Europe using three different models. All models were, however, based on the same input data. The analyses covered entire Europe, such that differences between regions and countries in Europe could be identified. This homogenous and objective analysis allowed comparing and ranking European countries in absolute or relative numbers of exposed land area, population and infrastructure. All models identified Italy as the country with the highest exposure to landslide risk. However, the small alpine countries had the highest relative exposure compared to their total land area and population. Overall, 4 to 7 million people in Europe, as well as significant amount of infrastructure are exposed to landslide threat. In the expectation of a changing climate, the question arises on how the level and spatial pattern of landslide hazard and risk in Europe will develop...
It is a common phenomenon that the next earthquake will test whether lessons from previous disasters became " Lessons-Learned " or they were simply ignored and forgotten. As a dramatic reality, repetition of lessons from... more
It is a common phenomenon that the next earthquake will test whether lessons from previous disasters became " Lessons-Learned " or they were simply ignored and forgotten. As a dramatic reality, repetition of lessons from earthquake disasters occurs in both time and space. To learn the lessons from two large earthquake disasters in Iran-Rudbar 1990 and Bam 2003 and also lessons from other six large earthquake disasters worldwide-requires a sustainable long-term framework, a culture of earthquake disaster risk reduction and a boost in the resilience of both rural and urban communities at risk. The Japanese model of such culture as an illustrative example and few practical suggestions for implementation are offered for the Iranian seismic space.
Thematic Issue: Natural disaster science – A Nordic approach to integrated research on disaster risk Abstract: Time is a crucial coordinate for seismology, though often its ubiquity is forgotten by society as it is taken for granted and... more
Thematic Issue: Natural disaster science – A Nordic approach to integrated research on disaster risk Abstract: Time is a crucial coordinate for seismology, though often its ubiquity is forgotten by society as it is taken for granted and its potential is unexplored within the arena of earthquake disaster risk reduction. Earthquake disasters build up over time. An earthquake is a dramatic context that takes just tiny units of time to bring an immense tragedy of human loss, suffering and destruction. This paper targets the exploration of the timescape for four large earthquake disasters in Iran: Bam in 2003, Rudbar in 1990, Tabas in 1978 and Buyin Zahra in 1962. An investigation of the intricacies of earthquake time and earthquake disaster time is performed for these four earthquake disasters which covers a time interval of 52 years. These large earthquake disasters are considered as chronological milestones for the Iranian seismic timescape. This contributes to model seismic patterns ...
The evaluation of the safety of natural or man-made slopes involves uncertainties. With a deterministic safety factor, the geotechnical engineer tries to deal with the uncertainties by choosing reasonably conservative parameters for... more
The evaluation of the safety of natural or man-made slopes involves uncertainties. With a deterministic safety factor, the geotechnical engineer tries to deal with the uncertainties by choosing reasonably conservative parameters for stability evaluation. The deterministic approach fails to deal consistently with uncertainties. As a complement to the deterministic approach, a probabilistic approach that allows for hazard and risk assessment of slopes is recommended. The paper proposes a framework integrating existing methods to exploit the benefits of the two approaches. Societal aspects, including allowable and tolerable risk, are briefly considered. The need for input on the social dimension of landslides, and the role of risk assessment in easing communication among the different experts are also discussed.
The heterogeneity of natural soils is well known in geotechnical practice. However, the importance of quantifying the resulting variability in geotechnical characterisation and design parameters is not adequately recognised. Variability... more
The heterogeneity of natural soils is well known in geotechnical practice. However, the importance of quantifying the resulting variability in geotechnical characterisation and design parameters is not adequately recognised. Variability should not be approached suspiciously. Rather, it should be accepted as a positive contribution to geotechnical design as its consistent modelling and utilisation lead, with limited additional computations and conceptual effort on the part of the engineer, to more rational and economic design. The paper presents a structured - though necessarily partial – review of approaches and methodologies for the quantification of soil variability, as well as selected examples of its utilisation in reliability-based geotechnical design.
Quantitative risk estimation for geohazards is frequently achieved through a reference framework which sees risk as the product of three macro-components: hazard, vulnerability and the value of elements at risk. Uncertainty-based risk... more
Quantitative risk estimation for geohazards is frequently achieved through a reference framework which sees risk as the product of three macro-components: hazard, vulnerability and the value of elements at risk. Uncertainty-based risk estimation provides a more complete assessment of risk in comparison with deterministic approaches, in which uncertainties in parameters and models are not addressed explicitly. While the hazard macro-component is inherently related to uncertainty, vulnerability and the value of elements at risk are most often addressed as deterministic parameters. A truly uncertainty-based analysis should, however, involve the non-deterministic characterization of all the macro-components of risk. The paper addresses the probabilistic estimation of risk for geohazards. The estimation of risk involves two main phases: (1) characterization of risk macro-components; and (2) calculation of risk by the reference framework. In a statistical-probabilistic perspective, both p...
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ABSTRACT This paper targets the handling of dead people after two earthquake disasters in Iran: Tabas and Bam. Both places are located in arid and semi-arid areas of Iran. The high death tolls had a powerful impact on the narratives of... more
ABSTRACT This paper targets the handling of dead people after two earthquake disasters in Iran: Tabas and Bam. Both places are located in arid and semi-arid areas of Iran. The high death tolls had a powerful impact on the narratives of Tabas and Bam survivors and witnesses. A thematic analysis of these narratives was performed, and various factors that impacted both the handling of dead people and the survivors' resilience were identified. The paradigmatic landscape of beliefs, rites and funerary rituals were accompanied by other factors, such people under debris, fears of epidemics, difficulty in accessing the water sources, looting, non-identification of dead people and no earthquake disaster awareness and preparedness. Beliefs and cultural traditions are seen as vital resources for the resilience, but they may shape differently the resilience of survivors and the disaster management for handling of dead bodies, and some beliefs may impact the resilience in two different ways. Furthermore, practical suggestions on the both handling of dead people and survivors' resilience are offered. The findings of this study adds to the lessons of handling dead people after earthquake disasters in Iran, to the agenda of earthquake disaster risk reduction and to the implementation of a sound disaster management and sustainable earthquake preparedness plans in Iran.
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RÉSUMÉ Un glissement massif sur les pentes rocheuses d'Åknes dans la municipalité de Stranda en Norvège pourrait avoir des con-séquences désastreuses, puisque le glissement pourrait générer un tsunami qui engloutirait plusieurs... more
RÉSUMÉ Un glissement massif sur les pentes rocheuses d'Åknes dans la municipalité de Stranda en Norvège pourrait avoir des con-séquences désastreuses, puisque le glissement pourrait générer un tsunami qui engloutirait plusieurs villages le long du fjord Storfjord. Reconnaissances de site, instrumentation et un système d'alerte ont été établis afin de protéger la population de la région. Une analyse par arbre à événements a été menée pour quantifier le hazard et le risque associés avec une rupture de pente suivie par un tsunami. L'analyse avait aussi pour but d'examiner les paramètres requis pour un système d'alerte pré-ventif fiable, et établir une liste de mesures pour réduire le risque. L'article décrit les problèmes géotechniques et les résul-tats d'une analyse de génération d'un tsunami. Il décrit la méthode d'analyse ETA (arbre à événements) et présente les premiers résultats de l'analyse. Un consensus d'opinions parmi des représentan...
Landslide risk must be assessed at the appropriate scale in order to allow effective risk management. At the moment, few deterministic models exist that can do all the computations required for a complete landslide risk assessment at a... more
Landslide risk must be assessed at the appropriate scale in order to allow effective risk management. At the moment, few deterministic models exist that can do all the computations required for a complete landslide risk assessment at a regional scale. This arises from the difficulty to precisely define the location and volume of the released mass and from the inability of the models to compute the displacement with a large amount of individual initiation areas (computationally exhaustive). This paper presents a medium-scale, dynamic physical model for rapid mass movements in mountainous and volcanic areas. The deterministic nature of the approach makes it possible to apply it to other sites since it considers the frictional equilibrium conditions for the initiation process, the rheological resistance of the displaced flow for the run-out process and fragility curve that links intensity to economic loss for each building. The model takes into account the triggering effect of an earth...
Landslide triggered by earthquakes is a serious threat for many communities around the world, and in some cases is known to have caused 25-50% of the earthquake fatalities. Seismic shaking can contribute to the triggering of debris flows... more
Landslide triggered by earthquakes is a serious threat for many communities around the world, and in some cases is known to have caused 25-50% of the earthquake fatalities. Seismic shaking can contribute to the triggering of debris flows either during the seismic event or indirectly by increasing the susceptibility of the slope to debris flow during intense rainfall in a period after the seismic event. The paper proposes a model to quantify both these effects. The model is based on an infinite slope formulation where precipitation and earthquakes influence the slope stability as follows: (1) During the shaking, the factor of safety is reduced due to cyclic pore pressure build-up where the cyclic pore pressure is modelled as a function of earthquake duration and intensity (measured as number of equivalent shear stress cycles and cyclic shear stress magnitude) and in-situ soil conditions (measured as average normalised shear stress). The model is calibrated using cyclic triaxial and d...
The reliability of pile foundations under severe environmental loading offshore depends on the uncertainty in the parameters in the analyses. To evaluate the required resistance factor for foundation design, the annual probability of... more
The reliability of pile foundations under severe environmental loading offshore depends on the uncertainty in the parameters in the analyses. To evaluate the required resistance factor for foundation design, the annual probability of failure was quantified for three jackets. The study included a statistical evaluation of the soil and load parameters and model uncertainty, the deterministic and probabilistic analyses of the ultimate axial pile capacity, the calculation of the annual probability of failure and the calibration of the required resistance factor for a target annual probability of failure of 10-4. The results show that the annual probability of failure varies with the axial pile capacity calculation method, and strongly depend on the model uncertainty applied.
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The 2004 Indian Ocean Tsunami has led to an increased awareness of tsunamis on a global level, and in particular in the South East Asian region. Emphasis has been on awareness as well as establishing warning system, and to a less degree... more
The 2004 Indian Ocean Tsunami has led to an increased awareness of tsunamis on a global level, and in particular in the South East Asian region. Emphasis has been on awareness as well as establishing warning system, and to a less degree on tsunami hazard and risk mapping. Notwithstanding, there is a need for quantifying the hazard and risk on
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Research Interests: Earth Sciences, Marine Geology, Monte Carlo Simulation, Slope Stability, Finite element method, and 12 moreRisk assessment, Finite Element, Gas Hydrate, Cyclic Loading, Continental Slope, Finite element simulation, Second Order, Shear Strength, North Sea, Risk Assessment, Large Scale, and Pore Pressure
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Assessment of seismic performance and estimation of permanent displacements for submerged slopes require the accurate description of the soil's stress–strain-strength relationship under irregular cyclic loading. The geological... more
Assessment of seismic performance and estimation of permanent displacements for submerged slopes require the accurate description of the soil's stress–strain-strength relationship under irregular cyclic loading. The geological profile of submerged slopes on the continental shelf typically consists of normally to lightly overconsolidated clays with depths ranging from a few meters to a few hundred meters and very low slope angles. This paper describes the formulation of a simplified effective-stress-based model, which is able to capture the key aspects of the cyclic behavior of normally consolidated clays. The proposed constitutive law incorporates anisotropic hardening and bounding surface principles to allow the user to simulate different shear strain and stress reversal histories as well as provide realistic descriptions of the accumulation of plastic shear strains and excess pore pressures during successive loading cycles.
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ABSTRACT Rainfall-triggered landslides pose a major threat to Central America and other landslide-prone regions. The development of new tools to understand and characterize landslide-triggering rainfall is a key aspect in the context of... more
ABSTRACT Rainfall-triggered landslides pose a major threat to Central America and other landslide-prone regions. The development of new tools to understand and characterize landslide-triggering rainfall is a key aspect in the context of hazard assessment and risk mitigation strategies. The purpose of this study is to present a new conceptual framework in which a connection is established between rainfall thresholds and landslide susceptibility, and to suggest three potential applications of this framework: (1) an empirical estimation of the probability of landslide-triggering rainfall; (2) a threshold-based time-trend analysis of rainfall series; (3) a susceptibility-based early warning system. The applications are illustrated with cases and data from tropical climates, with particular emphasis on cases with climatological and geological settings comparable with those in Central America.
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... It could also provide valuable insight in the variations of the properties of the soil. However, even if the parameters are constant with depth, by letting the small strain shear modulus vary, we ensure that the behavior of each layer... more
... It could also provide valuable insight in the variations of the properties of the soil. However, even if the parameters are constant with depth, by letting the small strain shear modulus vary, we ensure that the behavior of each layer will be different. ...
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Abstract Within the engineering profession and natural sciences, vulnerability is widely accepted to be defined as the degree of loss (or damage) to a given element or set of elements within the area affected by a threat. The value of... more
Abstract Within the engineering profession and natural sciences, vulnerability is widely accepted to be defined as the degree of loss (or damage) to a given element or set of elements within the area affected by a threat. The value of vulnerability is expressed ...
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ABSTRACT