Optically Stimulated Luminescence (OSL) Dating of Sediments from Himalaya

Optically Stimulated Luminescence (OSL) dating gives the age of most recent daylight exposure or heating of samples to >400 degrees C or the formation events of authigenic minerals. These correspond to the age of sedimentation and burial, ages of thermal events like contact heating by lava flows and heating during faulting and sand dyke formation, and the formation of a mineral via chemical precipitation. With the first observation of OSL in 1985, this method now occupies centre stage in Quaternary Geochronology. The use of OSL method for sediments from Himalaya began over three decades ago. The method has since provided chronology for a variety of events, such as past glaciation events, formation ages of river terraces, paleo-lacustrine deposits, landslides, floods, seismic events with substantive new insights into timing and style of geological processes. Theoretically, the dating range of method is present to a Million years, and this critically depends on two factors, viz, luminescence properties of mineral and their radiation environments. The general working range using quartz is 200ka, and using feldspars is up to Brunhes Matuyam Boundary. Extensions beyond this limit are currently being explored.

Macro-Level Assessment of Seismically Induced Landslide Hazard for the State of Sikkim, India Based On GIS Technique

This paper presents a macro-level seismic landslide hazard assessment for the entire state of Sikkim, India, based on the Newmark's methodology. The slope map of Sikkim was derived from ASTER Global Digital Elevation Model (GDEM). Seismic shaking in terms of peak horizontal acceleration (PHA) at bedrock level was estimated from deterministic seismic hazard analysis (DSHA), considering point source model. Peak horizontal acceleration at the surface level for the study area was estimated based on nonlinear site amplification technique, considering B-type NEHRP site class. The PHA at surface was considered to induce driving forces on slopes, thus causing landslides. Knowing the surface level PHA and slope angle, the seismic landslide hazard assessment for each grid point was carried out using Newmark's analysis. The critical static factor of safety required to resist landslide for the PHA (obtained from deterministic analysis) was evaluated and its spatial variation throughout the study area is presented. For any slope in the study area, if the in-situ (available) static factor of safety is greater than the static factor of safety required to resist landslide as predicted in the present study, that slope is considered to be safe.

Probabilistic Models for Forecasting Earthquakes in the Northeast Region of India

Northeast India and its adjoining areas are characterized by very high seismic activity. According to the Indian seismic code, the region falls under seismic zone V, which represents the highest seismic-hazard level in the country. This region has experienced a number of great earthquakes, such as the Assam (1950) and Shillong (1897) earthquakes, that caused huge devastation in the entire northeast and adjacent areas by flooding, landslides, liquefaction, and damage to roads and buildings. In this study, an attempt has been made to find the probability of occurrence of a major earthquake (M-w > 6) in this region using an updated earthquake catalog collected from different sources. Thereafter, dividing the catalog into six different seismic regions based on different tectonic features and seismogenic factors, the probability of occurrences was estimated using three models: the lognormal, Weibull, and gamma distributions. We calculated the logarithmic probability of the likelihood function (ln L) for all six regions and the entire northeast for all three stochastic models. A higher value of ln L suggests a better model, and a lower value shows a worse model. The results show different model suits for different seismic zones, but the majority follows lognormal, which is better for forecasting magnitude size. According to the results, Weibull shows the highest conditional probabilities among the three models for small as well as large elapsed time T and time intervals t, whereas the lognormal model shows the lowest and the gamma model shows intermediate probabilities. Only for elapsed time T = 0, the lognormal model shows the highest conditional probabilities among the three models at a smaller time interval (t = 3-15 yrs). The opposite result is observed at larger time intervals (t = 15-25 yrs), which show the highest probabilities for the Weibull model. However, based on this study, the IndoBurma Range and Eastern Himalaya show a high probability of occurrence in the 5 yr period 2012-2017 with >90% probability.

爆破方法识别滑带试验研究

以往对滑坡体中软弱层与滑带的识别主要依赖十钻孔并辅之以工程师的经验。采用在钻孔中进行爆破的方法，通过对地表接收信号的波形分析即可十分方便地识别出软弱层与滑带。简耍阐述了该方法的理论依据，通过对现场爆破实验测量信号的分析可以发现，该方法可以减少钻孔数量以及提高滑带识别的精度与效率。

A Dynamic Comprehensive Method for Landslide Control

A slope failure is developed due to progressive external loads and deteriorations of slope geomaterials, thus forming a progressive and dynamic development and occurrence of landslides. Site geological properties and other active factors such as hydrodynamic load and human activities are complex and usually unknown, thus this dynamic development and occurrence of landslides can only be understood through the progressive accumulation of knowledge on the landslides. For such a progressive process, this paper proposes a dynamic comprehensive control method for landslide control. This control method takes full advantage of updated monitoring data and site investigations of landslides, and emphasizes the implementation of possible measures for landslide control at reasonable stages and in different groups. These measures are to prevent the occurrence of a landslide disaster. As a case study, a landslide project at the Panluo open-pit iron mine is analyzed to illustrate this dynamic comprehensive control method.

Mechanism on Progressive Failure of a Faulted Rock Slope Due to Slip-Weakening

Slip-weakening is one of the characteristics of geological materials under certain loadings. Non-uniform rock structure may exist in the vicinity of the slip surface for a rock slope. Some portion of the slip surface may be penetrated but the other not. For the latter case, the crack or the fault surface will undergo shear deformation before it becomes a successive surface under a certain loading. As the slipped portion advances,slip-weakening occurs over a distance behind the crack tip. In the weakening zone, the shear strength will decrease from its peak value to residual friction level. The stress will redistribute along the surface of crack and in the weakening zone. Thus the changed local stress concentration leads the crack to extend and the ratio of penetration of the slip surface to increase. From the view of large-scale for the whole slip surface, the shear strength will decrease due to the damage of interior rock structure, and the faulted rock behaves as a softening material. Such a kind of mechanism performs in a large number of practical landslides in the zones experienced strong earthquakes. It should be noted that the mechanism mentioned above is different from that of the breakage of structural clay,in which the geological material is regarded as a medium containing structural lumps and structural bands. In this paper, the softening behavior of a faulted rock should be regarded as a comprehensive result of the whole complicated process including slip-weakening, redistribution of stress, extension of crack tip, and the penetration of the slip surface. This process is accompanied by progressive failure and abrupt structural damage. The size of slip-weakening zone is related to the undergoing strain. Once the relative slide is initiated (local or integrated), the effect of slip-weakening will behave in a certain length behind the crack tip until the formation of the whole slip surface.

Liquefaction and Displacement of Saturated Sand Under Vertical Vibration Loading

In order to investigate the influence of the vertical vibration loading on the liquefaction of saturated sand, one dimensional model for the saturated sand with a vertical vibration is presented based on the two phase continuous media theory. The development of the liquefaction and the liquefaction region are analyzed. It is shown that the vertical vibration loading could induce liquefaction. The rate of the liquefaction increases with the increase of the initial limit strain or initial porosity or amplitude and frequency of loading, and increases with the decrease of the permeability or initial modulus. It is shown also that there is a phase lag in the sand column. When the sand permeability distribution is non-uniform, the pore pressure and the strain will rise sharply where the permeability is the smallest, and fracture might be induced. With the development of liquefaction, the strength of the soil foundation becomes smaller and smaller. In the limiting case, landslides or debris flows could occur.

Arquitectura y funcionalidad del Gran Templo de Requem

Resumen: Hasta 1993 no se llevaron a cabo por primera vez las excavaciones en lo que prometía ser el emplazamiento de una de las construcciones más importantes de Petra, la impresionante capital del reino nabateo. Su edificación, cuya iniciación data del siglo I a.C., sufrió numerosas modificaciones, reconstrucciones y derrumbamientos a lo largo de sus más de quinientos años de funcionamiento. Pero a pesar de ello aun hoy se desconocen con certeza las funciones para las cuales fue diseñado ya que, al margen de los elementos constructivos, apenas se han localizado materiales y aun menos inscripciones que arrojen algo de luz a un problema sobre el que intentaremos aquí exponer diversas teorías que posibiliten un mayor acercamiento a su resolución.

Slope Stability Analysis Using Anisotropic and Nonlinear Failure Criteria

The shear strength of soils or rocks developed in a landslide usually exhibits anisotropic and nonlinear behavior. The process of sedimentation and subsequent consolidation can cause anisotropy of sedimentary soils or rocks, for instance. Nonlinearity of failure envelope could be attributed to "interlocking" or "dilatancy" of the material, which is generally dependent upon the stress level. An analytical method considering both anisotropy and nonlinearity of the failure envelops of soil and rocks is presented in the paper. The nonlinearfailure envelopes can be determined from routine triaxial tests. A spreadsheet program, which uses the Janbu's Generalized Procedure of Slice and incorporates anisotropic, illustrates the implementation of the approach and nonlinearfailure envelops. In the analysis, an equivalent Mohr-Coulomb linear failure criterion is obtained by drawing a tangent to the nonlinear envelope of an anisotropic soil at an appropriate stress level. An illustrative example is presented to show the feasibility and numerical efficiency of the method.

Cracks in saturated sand

The formation mechanism of water film (or crack) in saturated sand is analyzed numerically It is shown that there will be no stable "water film" in the saturated sand even if the strength of the skeleton is zero and no positions are choked. The stable water films initiate and grow if the choking state keeps unchangeable once the fluid velocities of one position decreases to zero in a liquefied sand column. A simplified method for evaluating the thickness of water film is presented according to a solidification wave theory. The theoretical results obtained by the simplified method are compared with the numerical results and the experimental results of Kokusho.

Effects of rainfall infiltration on the stability of soil slopes

Slope failure due to rainfall is a common geotechnical problem. The mechanics of rainfall induced landslides involves the interaction of a number of complex hydrologic and geotechnical factors. This study attempts to identify the influence of some of these factors on the stability of soil slope including rainfall intensity, hydraulic conductivity and the strength parameters of soil.

Studying conscious and unconscious vision with functional Magnetic Resonance Imaging : the BOLD promise

Waking up from a dreamless sleep, I open my eyes, recognize my wife’s face and am filled with joy. In this thesis, I used functional Magnetic Resonance Imaging (fMRI) to gain insights into the mechanisms involved in this seemingly simple daily occurrence, which poses at least three great challenges to neuroscience: how does conscious experience arise from the activity of the brain? How does the brain process visual input to the point of recognizing individual faces? How does the brain store semantic knowledge about people that we know? To start tackling the first question, I studied the neural correlates of unconscious processing of invisible faces. I was unable to image significant activations related to the processing of completely invisible faces, despite existing reports in the literature. I thus moved on to the next question and studied how recognition of a familiar person was achieved in the brain; I focused on finding invariant representations of person identity – representations that would be activated any time we think of a familiar person, read their name, see their picture, hear them talk, etc. There again, I could not find significant evidence for such representations with fMRI, even in regions where they had previously been found with single unit recordings in human patients (the Jennifer Aniston neurons). Faced with these null outcomes, the scope of my investigations eventually turned back towards the technique that I had been using, fMRI, and the recently praised analytical tools that I had been trusting, Multivariate Pattern Analysis. After a mostly disappointing attempt at replicating a strong single unit finding of a categorical response to animals in the right human amygdala with fMRI, I put fMRI decoding to an ultimate test with a unique dataset acquired in the macaque monkey. There I showed a dissociation between the ability of fMRI to pick up face viewpoint information and its inability to pick up face identity information, which I mostly traced back to the poor clustering of identity selective units. Though fMRI decoding is a powerful new analytical tool, it does not rid fMRI of its inherent limitations as a hemodynamics-based measure.

Mapeamento geológico em áreas graníticas intemperizadas em regiões montanhosas tropicais: o granito Conselheiro Paulino (Faixa Ribeira)

Neste trabalho foram integrados o mapeamento geológico de campo, os dados regionais aerogeofísicos e as imagens orbitais de alta resolução (1 m) para fornecer um mapa geológico detalhado do Pluton granítico Conselheiro Paulino, na Faixa Ribeira, Brasil. A área estudada possui poucos afloramentos e outras questões que dificultam o mapeamento geológico tradicional. Escorregamentos de terra são comuns na porção mais intemperizada do granito. A utilização de imagens orbitais de alta resolução permitiu a identificação dos poucos afloramentos existentes, além de outros elementos, como ravinas, planícies aluviais, eluviões, vegetação e estradas. Isso foi importante para orientar e otimizar as pesquisas de campo. A disponibilidade de dados aerogeofísicos magnéticos e radiométricos corroboraram nos trabalhos de campo e na petrografia do Pluton granítico Conselheiro Paulino. O pluton pode ser dividido em duas facies distintas, sendo uma de composição microgranítica e outra de composição microgranodiorítica

Região Serrana do Estado do Rio de Janeiro e a expansão dos riscos ambientais, ações preventivas e catástrofes: o caso de Petrópolis

O município de Petrópolis, palco de recorrente de problemas ambientais envolvendo movimentos de massa concentrados historicamente na sua área mais urbanizada, os distritos Sede e Cascatinha, vive nas últimas décadas um crescimento populacional que se orienta basicamente para antigas áreas rurais de Itaipava, Pedro do Rio e Posse. O objetivo geral da pesquisa é investigar como este crescimento vem ocorrendo, analisando as características geológico-geomorfológicas dos novos espaços ocupados, os fatores predisponentes às novas condições de risco envolvendo os movimentos de massa e as inundações. Assim, foi elaborado um panorama sócio-evolutivo do processo de ocupação do solo em Petrópolis, considerando especialmente a dinâmica demográfica registrada nos distritos através dos censos demográficos a partir da década de 1940. Utilizando o geoprocessamento como ferramenta e a classificação visual de segmentação de OrtofotosCarta IBGE na escala 1: 25.000, foram produzidos mapas de uso do solo para o município e distritos detalhando a área ocupada. Com o fim de atender ao diagnóstico das situações de risco foi realizado o levantamento da situação atual da ocorrência dos movimentos de massa e inundações no município, comparando levantamentos anteriores e verificando a distribuição das ocorrências e a população atingida. Por fim, a avaliação da execução da política de desenvolvimento e expansão urbana definida no Plano Diretor de Petrópolis e na Lei de Uso, Parcelamento e Ocupação do Solo, analisando o zoneamento e seus usos (rural, rururbano, urbano e zona de proteção especial) resultando no entendimento de como os aspectos normativos vem sendo tratados, naquilo que são respeitados e naquilo que não são cumpridos na dinâmica da ocupação do espaço, levantando as ações de prevenção, ou não, dos problemas ambientais. Contudo, a definição dos objetivos do trabalho teve dois momentos. O primeiro com a análise da expansão urbana construindo novas condições de risco e o segundo momento, lamentavelmente, aquele no qual as evidências ganharam contorno de realidade com o ocorrido em dezembro de 2010 e em janeiro de 2011, principalmente quando inundações bruscas associadas aos deslizamentos de terra nas encostas atingiram áreas de Petrópolis e de outros municípios da região Serrana do Estado do Rio de Janeiro, certamente, a maior tragédia ambiental ocorrida no Centro-Sul do país até então. Com mais de 900 mortos, centenas de desaparecidos e milhares de desabrigados e desalojados, os eventos suplantaram os objetivos do trabalho, colocando novas questões, ao mesmo tempo em que a realidade demonstrou a coerência e pertinência daqueles objetivos com os problemas apresentados. Assim, dentre os objetivos passou a constar também a verificação in loco das conseqüências de movimentos de massa e inundações nas áreas apontadas anteriormente, como foi o caso do vale do Rio Santo Antônio em Itaipava. O trabalho, assim, se pautou por indicar a necessidade ter-se maior atenção às novas áreas de ocupação no município, considerando a natureza do território, contribuindo como um subsídio na prevenção ao risco.