Earthquake-induced sliding displacements are commonly used to assess the seismic performance of slopes. These displacements represent the cumulative, downslope movement of a sliding block due to earthquake shaking. While the sliding block model is a simplified representation of the field conditions, the displacements predicted from this model have been shown to be a useful index of seismic performance of slopes. Current evaluation procedures that use sliding block displacements to evaluate the potential for slope instability typically are based on a deterministic approach or a pseudo-probabilistic approach, in which the variabilities in the expected ground motion and predicted displacement are either ignored or not treated rigorously. Thus, there is no concept of the actual hazard (i.e., the annual probability of exceedance) associated with the computed displacement. This dissertation focuses on quantifying the risk for earthquake-induced landslides. The basic approach involves a probabilistic framework for computing the annual rate of exceedance of different levels of sliding displacement for a slope such that a hazard curve for sliding displacement can be developed. The framework incorporates the uncertainties in the prediction of earthquake ground shaking, in the prediction of sliding displacement, and in the assessment of soil properties. The framework considers two procedures that will yield a displacement hazard curve: the scalar hazard approach that utilizes a single ground motion parameter and its associated hazard curve to compute permanent sliding displacements; and a vector hazard approach that predicts displacements based on two (or more) ground motion parameters and the correlation between these parameters. Current predictive models for sliding displacement provide the expected level of displacement as a function of the characteristics of the slope (e.g., geometry, strength, yield acceleration) and the characteristics of earthquake shaking (e.g., peak ground acceleration, peak ground velocity). However, current models contain significant aleatory variability such that the range of predicted displacements is large. To reduce the variability in the sliding displacement prediction and to provide models appropriate for the presented probabilistic framework, sliding displacement predictive equations are developed that utilize single and multiple ground motion parameters. The developed framework is implemented to the Mint Canyon 7.5-minute quadrangle in California to generate a map of earthquake-induced landslide hazard. Application of the probabilistic procedure to a 7-1/2 minute quadrangle of California is an important exercise to identify potential difficulties in California Geological Survey’s (CGS) current application for hazard mapping, and for the eventual adoption by CGS and USGS. / text

Earthquake-induced landslides are a significant seismic hazard that can generate large economic losses. Predicting earthquake-induced landslides often involves an assessment of the expected sliding displacement induced by the ground shaking. A deterministic approach is commonly used for this purpose. This approach predicts sliding displacements using the expected ground shaking and the best-estimate slope properties (i.e., soil shear strengths, ground water conditions and thicknesses of sliding blocks), and does not consider the aleatory variability in predictions of ground shaking or sliding displacements or the epistemic uncertainties in the slope properties. In this dissertation, a probabilistic framework for predicting the sliding displacement of flexible sliding masses during earthquakes is developed. This framework computes a displacement hazard curve using: (1) a ground motion hazard curve from a probabilistic seismic hazard analysis, (2) a model for predicting the dynamic response of the sliding mass, (3) a model for predicting the sliding response of the sliding mass, and (4) a logic tree that incorporates the uncertainties in the various input parameters. The developed probabilistic framework for flexible sliding masses is applied to a slope at a site in California. The results of this analysis show that the displacements predicted by the probabilistic approach are larger than the deterministic approach due to the influence of the uncertainties in the slope properties. Reducing these uncertainties can reduce the predicted displacements. Regional maps of seismic landslide potential are used in land-use planning and to identify zones that require detailed, site-specific studies. Current seismic landslide hazard mapping efforts typically utilize deterministic approaches to estimate rigid sliding block displacements and identify potential slope failures. A probabilistic framework that uses displacement hazard curves and logic-tree analysis is developed for regional seismic landslide mapping efforts. A computationally efficient approach is developed that allows the logic-tree approach to be applied for regional analysis. Anchorage, Alaska is used as a study area to apply the developed approach. With aleatory variability and epistemic uncertainties considered, the probabilistic map shows that the area of high/very high hazard of seismic landslides increases by a factor of 3 compared with a deterministic map. / text

Regional landslide risk, as it is most commonly defined, is a product of the following: hazard, vulnerability and exposed population. The first objective of this research project is to estimate the regional landslide hazard level by calculating its probability of slope failure based on maximum slope angles, as estimated using data provided by digital elevation models (DEM). Furthermore, it addresses the impact of DEM resolution on perceived slope angles, using local averaging theory, by comparing the results predicted from DEM datasets of differing resolutions. Although the likelihood that a landslide will occur can be predicted with a hazard assessment model, the extent of the damage inflicted upon a region is a function of vulnerability. This introduces the second objective of this research project: vulnerability assessment. The third and final objective concerns the impact of urbanization and population growth on landslide risk levels.

Case study analysis of the 2010-2011 Canterbury Earthquake Sequence (CES), which particularly impacted Christchurch City, New Zealand, has highlighted the value of practical, standardised and coordinated post-earthquake geotechnical response guidelines for earthquake-induced landslides in urban areas. The 22nd February 2011 earthquake, the second largest magnitude event in the CES, initiated a series of rockfall, cliff collapse and loess failures around the Port Hills which severely impacted the south-eastern part of Christchurch. The extensive slope failure induced by the 22nd February 200 earthquake was unprecedented; and ground motions experienced significantly exceeded the probabilistic seismic hazard model for Canterbury. Earthquake-induced landslides initiated by the 22nd February 2011 earthquake posed risk to life safety, and caused widespread damage to dwellings and critical infrastructure. In the immediate aftermath of the 22nd February 2011 earthquake, the geotechnical community responded by deploying into the Port Hills to conduct assessment of slope failure hazards and life safety risk. Coordination within the voluntary geotechnical response group evolved rapidly within the first week post-earthquake. The lack of pre-event planning to guide coordinated geotechnical response hindered the execution of timely and transparent management of life safety risk from coseismic landslides in the initial week after the earthquake. Semi-structured interviews were conducted with municipal, management and operational organisations involved in the geotechnical response during the CES. Analysis of interview dialogue highlighted the temporal evolution of priorities and tasks during emergency response to coseismic slope failure, which was further developed into a phased conceptual model to inform future geotechnical response. Review of geotechnical responses to selected historical earthquakes (Northridge, 1994; Chi-Chi, 1999; Wenchuan, 2008) has enabled comparison between international practice and local response strategies, and has emphasised the value of pre-earthquake preparation, indicating the importance of integration of geotechnical response within national emergency management plans. Furthermore, analysis of the CES and international earthquakes has informed pragmatic recommendations for future response to coseismic slope failure. Recommendations for future response to earthquake-induced landslides presented in this thesis include: the integration of post-earthquake geotechnical response with national Civil Defence and Emergency Management; pre-earthquake development of an adaptive management structure and standard slope assessment format for geotechnical response; and emergency management training for geotechnical professionals. Post-earthquake response recommendations include the development of geographic sectors within the area impacted by coseismic slope failure, and the development of a GIS database for analysis and management of data collected during ground reconnaissance. Recommendations provided in this thesis aim to inform development of national guidelines for geotechnical response to earthquake-induced landslides in New Zealand, and prompt debate concerning international best practice.

The Haast Pass highway has had a long history of instability since it was constructed in 1960. Steep slopes and deeply incised river create an actively changing geomorphic environment making maintaining the highway corridor hazardous and difficult. This thesis study provides the first comprehensive investigation of the highway corridor between the Summit and Thunder Creek Falls using LiDAR and detailed air-photo analysis to provide the basis for geomorphic mapping. Management of slope hazards to date has been based on a reactive approach treating the immediate unstable areas around landslides after they occur. This study presents the first large-scale geomorphological assessment of the highway corridor identifying surface unit type, slope processes and slope hazards in order to facilitate the development of a long-term highway management strategy. Because dense vegetation covers nearly all the slopes above the highway in the study area as as such, it has not been possible to adequately investigate slope geomorphology until the availability of LiDAR. This study is the first to use Light direction and ranging[LiDAR] for corridor hazard mapping beneath dense vegetation in New Zealand. The LiDAR survey was flown by New Zealand Aerial Mapping in January 2014 for the New Zealand Transport Agency and was provided for use in this study. The LiDAR surface model created serves as the basis for mapping surface units and landslide features, enabling the identification of slope processes and landslide hazards. Aerial photos were also used to identify surface unit type and slope processes where vegetation was absent and enabled the activity of slopes to be evaluated. Interpretations made using LiDAR were validated using aerial photography and targeted ground truthing with all ground truthing sites confirming the interpretations made. Large scale geomorphology mapping was undertaken on slopes above the highway on the western side of the valley and showed that there were distinct differences between the southern and northern parts of the highway corridor. Between The Haast Pass Summit and Pipson Creek the slopes are dominated by schist bedrock with regolith confined to small deposits next to the highway and larger deposits in tributary valleys. The slope hazards affecting the highway in this zone are confined to debris sliding and rockfall from regolith deposits and bedrock cliffs next to the highway between Robinson and Pipson Creeks. The slopes between Pipson Creek and the Gates of Haast, in contrast, consist of deep regolith deposits and regolith veneered slopes. Evidence of active and recently active slope processes on the slopes facing the highway confirm the instability is associated with slope hazards including debris flows, debris slides, rock fall and highway collapse. Small-scale detailed evaluations were undertaken at Diana Falls, Ford Creek, The Hinge and the Gates of Haast with the sites selected based on their history of instability and/or their particu- larly hazardous appearance during the large-scale geomorphology and hazard identification. Using the LiDAR surface model surface units and landslide features were identified and mapped with small-scale engineering geomorphology maps. This information was then used to interpret the subsurface geometry and the failure mode/slope processes acting on the slope enabling an assessment of the current stability and future slope development to be made. Diana Falls was found to have scarps and tension cracks running across the regolith covered slope indicating that future landslides from this site will be an ongoing problem. At Ford Creek the landslide was identified as a rock compound slide, but assessments of its current stability and future development were unable to be made. Detailed investigations at The Hinge revealed evidence of a large creeping debris slide and the existence smaller debris slides below the highway through the entire investigation area; the debris slides identified show signs of activity and continued debris sliding will continue to affect the highway in the future. The investigation of the Gates of Haast revealed that the slope instability is not as extensive as it has been in the past, however, recent rock slides and debris flows have continued affect the highway and will continue to pose a hazard in the future. This thesis provides fundamental information required to develop a comprehensive management plan for the Haast Pass highway corridor between the Haast Pass summit and the Gates of Haast. A new landslide management plan has been developed outlining immediate, short-term and long- term options and programmes that should be implemented. Immediate options are steps that can be taken to quickly increase the safety of road users and include moving of highway closure gates and installation of warning signage. Short-term options aim to mitigate landslide hazards where feasible including the installation of rockfall barriers and debris flow attenuators, and lay the groundwork for future avoidance of hazards by undertaking investigations of highway realignment and developing highway closure rainfall thresholds. Long-term options are recommended where landslides will continue to impact the same section of the highway repeatedly and focus on hazard avoidance by building landslide shelters or major highway realignments. The adoption of a management plan ensures security of the highway, protects against loss of life and provides the most cost effective long-term solution to manage the landsliding hazards.

Empirically-based models of landslide distribution and susceptibility are currently the most commonly used approach for mapping probabilities of landslide initiation and analyzing their association with natural and anthropogenic environmental factors. In general, these models statistically estimate susceptibility based on the predisposition of an area to experience a landslide given a range of environmental factors, which may include land use, topography, hydrology and other spatial attributes. Novel statistical approaches include the generalized additive model (GAM), a non-parametric regression technique, which is used in this study to explore the relationship of landslide initiation to topography, rainfall and forest land cover and logging roads on Vancouver Island, British Columbia. The analysis is centered on an inventory of 639 landslides of winter 2006/07. Data sources representing potentially relevant environmental conditions of landslide initiation are based on: terrain analysis derived from a 20-m CDED digital elevation model; forest land cover classified from Landsat TM scenes for the summer before the 2006 rainy season; geostatistically interpolated antecedent rainfall patterns representing different temporal scales of rainfall (a major storm, winter and annual rainfall); and the main lithological units of surface geology. In order to assess the incremental effect of these data sources to predict landslide susceptibility, predictive performances of models based on GAMs are compared using spatial cross-validation estimates of the area under the ROC curve (AUROC), and variable selection frequencies are used to determine the prevalence of non-parametric associations to landslides. In addition to topographic variables, forest land cover (e.g., deforestation), and logging roads showed a strong association with landslide initiation, followed by rainfall patterns and the very general lithological classification as less important controls of landscape-scale landslide activity in this area. Annual rainfall patterns are found not to contribute significantly to model prediction improvement and may lead to model overfitting. Comparisons to generalized linear models (i.e., logistic regression) indicate that GAMs are significantly better for modeling landslide susceptibility. Overall, based on the model predictions, the most susceptible 4% of the study area had 29 times higher density of landslide initiation points than the least susceptible 73% of the study area (0.156 versus 0.005 landslides/km2).

Masters Research - Master of Science / Recent flash floods and landslides in the Philippines have caused many fatalities, loss of livelihoods; destroyed infrastructures, damaged natural resources and displaced several communities. Investigation of five disaster cases of flash floods and landslides from 1991 to 2006 was undertaken to gain an understanding of the causes, behaviour, distribution and biophysical impacts of these recurrent natural hazards. Sustaining healthy and resilient communities and protecting the ecosystem from natural disasters is a key development goal. Therefore, communities at risk need to adequately prepare for, respond to, and recover from the impacts of these natural disasters. A theory model on community resilience called the Landslip-Disaster Quadrant Model was developed to examine the capacity for resilience and the vulnerability of threatened communities. Six building blocks comprise this Model. A community study of the February 17, 2006 landslides in St. Bernard, Southern Leyte, was conducted to test and refine this Model. Major findings of the study have revealed that flash floods and landslides have been frequent due to changing climatic patterns and greater interaction of natural processes. Extreme weather conditions have resulted in intense rainfall that seeps through fractures and cracks in the ground. Rains saturate and loosen soil particles, weaken slope resistance, triggering landslides that formed natural dams. Failure of these natural dams or log jams caused flash floods and debris flows. The rapidity and destructiveness of these hazards were influenced by the angular position of sliding materials, slope resistance, type of cascading materials caught in the flow, river channel configuration, and human structures that obstruct and/or intensify overflow. These were the physical conditions of vulnerability to disasters in the five cases of natural disaster investigated. Rural livelihoods and the economic base of the local people in Saint Bernard, Southern Leyte, were limited and subsistent. Though the local people have a high literacy rate, they have inadequate understanding of the natural processes associated with landslides. Natural observations such as receding water levels in the river, fractures and cracks in the ground on the mountain, excessive rains and landslides in nearby communities could have been used as early warnings by the local people and authorities for safe evacuation. Many lives in Guinsaugon village could have thus been saved from the deadly landslides of 17 February 2006. Political interests have affected progress of resettlement housing and development projects that obliged many local people to extend the period spent living in the evacuation centres. However, the local people were expressive of their faith and hope to rise from the tragedy. These ‘bouncing back’ attitudes of the local people were indicative of their strong cultural values that formed the core of their coping capacity for natural disasters. The results of the community study tested and refined the Landslip-Disaster Quadrant Model. Among the six blocks for building a disaster-resilient community, cultural values and local norms ranked first. This is followed by ecological security, then livelihood sufficiency and economic base, and further by human health and wellness. The last two blocks were structural networks and institutional arrangements, and political will and priorities. This Model could form the framework for a Comprehensive Landslide and Flash Flood Disaster Risk Assessment in the Philippines. The community assessment toolkit developed in this study could be expanded further into policy and planning guidelines of the National Disaster Coordinating Council of the Philippines.

Thesis (M.A.)--University of Montana, 2008. / Title from title screen. Description based on contents viewed Aug. 19, 2008. Includes bibliographical references (p. 86-91).

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains vii, 129 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references (p. 79-86).

Thesis (Ph. D.)--Oregon State University, 1997. / Typescript (photocopy). Includes bibliographical references (leaves 259-268). Also available on the World Wide Web.