Debris flows in the southern Coast Mountains exhibit different dynamic and sedimentologic characteristics, depending on the lithology of their source areas. Fine-textured debris flows originating in the Quaternary volcanic complexes are much more mobile than those originating in the coarse-textured plutonic rocks which form most of this mountain range. Mobility can be described as the velocity of flow, the distance of travel of debris flows, and the slope required to sustain flow. The objectives of this study are to examine the effect of different sediment composition on the mobility of debris flows, and to determine which rheologic models are most applicable for modeling debris flows in these geologic environments. About 25 debris flow events in or adjacent to the southern Coast Mountains were examined, ranging in volume from 10² m³ to over 10⁷ m³. Field methods included sampling of grain-size distribution, measurement of the deposit and channel dimensions, and observation of the stratigraphy of debris flow fans. Shear strength, permeability, and consolidation tests were performed on samples of reconstituted debris, representative of typical fine-textured and coarsetextured debris flows. These samples were also used to model debris flows in a flume. The coarse-textured, plutonic-source, debris flows typically had a distinct, inverselygraded, clast-supported, surface layer of cobbles and boulders. Their deposits tended to be irregular in thickness, with lobes and levees of coarse material. The fine-textured, volcanicsource, debris flows had no such surface layer, and their deposits were generally uniform in thickness and surface morphology. These observations, and corroborating evidence from the flume results, suggest that fine-textured debris flows behave according to the Bingham flow model, while coarse-textured debris flows can be better described by a granular, or dilatant, flow model. A clay content of about 4% in the matrix (sub-4 mm material) is a useful measure to distinguish the two populations. Several debris flow events of intermediate behaviour and sediment composition were also examined. The permeability of the debris, and hence its rate of consolidation, is an important factor controlling mobility. The volume of debris flow events was found to be the most significant factor controlling runout distance.

Thesis (MS)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: David Varricchio. Includes bibliographical references (leaves 92-104).

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 94-105).

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [291]-305).

Debris flows in the southern Coast Mountains exhibit different dynamic and sedimentologic characteristics, depending on the lithology of their source areas. Fine-textured debris flows originating in the Quaternary volcanic complexes are much more mobile than those originating in the coarse-textured plutonic rocks which form most of this mountain range. Mobility can be described as the velocity of flow, the distance of travel of debris flows, and the slope required to sustain flow. The objectives of this study are to examine the effect of different sediment composition on the mobility of debris flows, and to determine which rheologic models are most applicable for modeling debris flows in these geologic environments. About 25 debris flow events in or adjacent to the southern Coast Mountains were examined, ranging in volume from 10² m³ to over 10⁷ m³. Field methods included sampling of grain-size distribution, measurement of the deposit and channel dimensions, and observation of the stratigraphy of debris flow fans. Shear strength, permeability, and consolidation tests were performed on samples of reconstituted debris, representative of typical fine-textured and coarsetextured debris flows. These samples were also used to model debris flows in a flume. The coarse-textured, plutonic-source, debris flows typically had a distinct, inverselygraded, clast-supported, surface layer of cobbles and boulders. Their deposits tended to be irregular in thickness, with lobes and levees of coarse material. The fine-textured, volcanicsource, debris flows had no such surface layer, and their deposits were generally uniform in thickness and surface morphology. These observations, and corroborating evidence from the flume results, suggest that fine-textured debris flows behave according to the Bingham flow model, while coarse-textured debris flows can be better described by a granular, or dilatant, flow model. A clay content of about 4% in the matrix (sub-4 mm material) is a useful measure to distinguish the two populations. Several debris flow events of intermediate behaviour and sediment composition were also examined. The permeability of the debris, and hence its rate of consolidation, is an important factor controlling mobility. The volume of debris flow events was found to be the most significant factor controlling runout distance. / Arts, Faculty of / Geography, Department of / Graduate

Rock-ice avalanches are three-phase flows composed of rock, ice, and a liquid. As their occurrences might increase in the future due to climate change, constructing mathematical and numerical models able to simulate these flows could be necessary for good hazard assessment and management in cold mountainous regions. With this aim, in this work, a framework of simplified rock-ice avalanche models is derived from a complete three-phase approach by applying two assumptions. Thanks to these two hypotheses, we obtain five classes of simplified mathematical models that simplify the rock- ice avalanche physics with different levels of approximation. Among these simplified approaches, the mathematical model, which simplifies the flow dynamics to a lesser extent, is a new mathematical model for rock-ice avalanches. For numerical purposes, a detailed analysis of the eigenvalues is performed for the one-dimensional depth-integrated version of the proposed model. Results show that the proposed approach loses hyperbolicity for specific ranges of the flow variables. Due to this feature, numerical modelling is performed by maintaining the numerical solutions in the hyperbolic domain of the flow variables. In this way, we consider the uniformly accelerated flow and the small perturbation of the flow depth and ice concentration as test cases. Additionally, we implement three numerical methods to identify the numerical scheme that can solve the proposed model accurately and to compare the obtained numerical results with those associated with the other simplified rock-ice avalanche approaches. Finally, we apply the linear stability theory to the proposed model to investigate its potential ill-posedness in the ranges of the flow variables where hyperbolicity is lost. Since the proposed approach turns out to be ill-posed, the model regularization is performed by trying to recover its hyperbolicity through a strategy suggested for a two- phase gas-liquid model. Although this strategy can enlarge the hyperbolic flow-variable range, hyperbolicity is still lost for specific flow conditions.

In hippocampal CA1 and CA3 regions, various properties of neuronal activity follow skewed, lognormal-like distributions, including average firing rates, rate and magnitude of spike bursts, magnitude of population synchrony, and correlations between pre- and postsynaptic spikes. In recent studies, the lognormal features of hippocampal activities were well replicated by a multi-timescale adaptive threshold (MAT) neuron network of lognormally distributed excitatory-to-excitatory synaptic weights, though it remains unknown whether and how other neuronal and network properties can be replicated in this model. Here we implement two additional studies of the same network: first, we further analyze its burstiness properties by identifying and clustering neurons with exceptionally bursty features, once again demonstrating the importance of the lognormal synaptic weight distribution. Second, we characterize dynamical patterns of activity termed neuronal avalanches in in vivo CA3 recordings of behaving rats and in the model network, revealing the similarities and differences between experimental and model avalanche size distributions across the sleep-wake cycle. These results show the comparison between the MAT neuron network and hippocampal readings in a different approach than shown before, providing more insight into the mechanisms behind activity in hippocampal subregions. / Nas regiões CA1 e CA3 do hipocampo, várias propriedades da atividade neuronal seguem distribuições assimétricas com características lognormais, incluindo frequência de disparo média, frequência e magnitude de rajadas de disparo (bursts), magnitude da sincronia populacional e correlações entre disparos pré- e pós-sinápticos. Em estudos recentes, as características lognormais das atividades hipocampais foram bem reproduzidas por uma rede de neurônios de limiar adaptativo (multi-timescale adaptive threshold, MAT) com pesos sinápticos entre neurônios excitatórios seguindo uma distribuição lognormal, embora ainda não se saiba se e como outras propriedades neuronais e da rede podem ser replicadas nesse modelo. Nesse trabalho implementamos dois estudos adicionais da mesma rede: primeiramente, analisamos mais a fundo as propriedades dos bursts identificando e agrupando neurônios com capacidade de burst excepcional, mostrando mais uma vez a importância da distribuição lognormal de pesos sinápticos. Em seguida, caracterizamos padrões dinâmicos de atividade chamados avalanches neuronais no modelo e em aquisições in vivo do CA3 de roedores em atividades comportamentais, revelando as semelhanças e diferenças entre as distribuições de tamanho de avalanche através do ciclo sono-vigília. Esses resultados mostram a comparação entre a rede de neurônios MAT e medições hipocampais em uma abordagem diferente da apresentada anteriormente, fornecendo mais percepção acerca dos mecanismos por trás da atividade em subregiões hipocampais.

In hippocampal CA1 and CA3 regions, various properties of neuronal activity follow skewed, lognormal-like distributions, including average firing rates, rate and magnitude of spike bursts, magnitude of population synchrony, and correlations between pre- and postsynaptic spikes. In recent studies, the lognormal features of hippocampal activities were well replicated by a multi-timescale adaptive threshold (MAT) neuron network of lognormally distributed excitatory-to-excitatory synaptic weights, though it remains unknown whether and how other neuronal and network properties can be replicated in this model. Here we implement two additional studies of the same network: first, we further analyze its burstiness properties by identifying and clustering neurons with exceptionally bursty features, once again demonstrating the importance of the lognormal synaptic weight distribution. Second, we characterize dynamical patterns of activity termed neuronal avalanches in in vivo CA3 recordings of behaving rats and in the model network, revealing the similarities and differences between experimental and model avalanche size distributions across the sleep-wake cycle. These results show the comparison between the MAT neuron network and hippocampal readings in a different approach than shown before, providing more insight into the mechanisms behind activity in hippocampal subregions. / Nas regiões CA1 e CA3 do hipocampo, várias propriedades da atividade neuronal seguem distribuições assimétricas com características lognormais, incluindo frequência de disparo média, frequência e magnitude de rajadas de disparo (bursts), magnitude da sincronia populacional e correlações entre disparos pré- e pós-sinápticos. Em estudos recentes, as características lognormais das atividades hipocampais foram bem reproduzidas por uma rede de neurônios de limiar adaptativo (multi-timescale adaptive threshold, MAT) com pesos sinápticos entre neurônios excitatórios seguindo uma distribuição lognormal, embora ainda não se saiba se e como outras propriedades neuronais e da rede podem ser replicadas nesse modelo. Nesse trabalho implementamos dois estudos adicionais da mesma rede: primeiramente, analisamos mais a fundo as propriedades dos bursts identificando e agrupando neurônios com capacidade de burst excepcional, mostrando mais uma vez a importância da distribuição lognormal de pesos sinápticos. Em seguida, caracterizamos padrões dinâmicos de atividade chamados avalanches neuronais no modelo e em aquisições in vivo do CA3 de roedores em atividades comportamentais, revelando as semelhanças e diferenças entre as distribuições de tamanho de avalanche através do ciclo sono-vigília. Esses resultados mostram a comparação entre a rede de neurônios MAT e medições hipocampais em uma abordagem diferente da apresentada anteriormente, fornecendo mais percepção acerca dos mecanismos por trás da atividade em subregiões hipocampais.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 70-74). Also available on the World Wide Web.

Thesis (M.Sc.)--Memorial University of Newfoundland, 1999. / Bibliography: leaves 87-94. Also available online.