Segmentation of the Himalayas as revealed by arc-parallel gravity anomalies

International audienceLateral variations along the Himalayan arc are suggested by an increasing number of studies and carry important information about the orogen’s segmentation. Here we compile the hitherto most complete land gravity dataset in the region which enables the currently highest resolution plausible analysis. To study lateral variations in collisional structure we compute arc-parallel gravity anomalies (APaGA) by subtracting the average arc-perpendicular profile from our dataset; we compute likewise for topography (APaTA). We find no direct correlation between APaGA, APaTA and background seismicity, as suggested in oceanic subduction context. In the Himalayas APaTA mainly reflect relief and erosional effects, whereas APaGA reflect the deep structure of the orogen with clear lateral boundaries. Four segments are outlined and have disparate flexural geometry: NE India, Bhutan, Nepal & India until Dehradun, and NW India. The segment boundaries in the India plate are related to inherited structures, and the boundaries of the Shillong block are highlighted by seismic activity. We find that large earthquakes of the past millennium do not propagate across the segment boundaries defined by APaGA, therefore these seem to set limits for potential rupture of megathrust earthquakes

Endemic transmission of visceral leishmaniasis in Bhutan

Visceral leishmaniasis was first reported in Bhutan in 2006. We conducted studies of the parasite, possible vectors and reservoirs, and leishmanin skin test and risk factor surveys in three villages. Nineteen cases were reported from seven districts. Parasite typing yielded two novel microsatellite sequences, both related to Indian L. donovani. In one case village, 40 (18.5%) of 216 participants had positive leishmanin skin test results, compared with 3 (4.2%) of 72 in the other case village and 0 of 108 in the control village. Positive results were strongly associated with the village and increasing age. None of the tested dogs were infected. Eighteen sand flies were collected, 13 Phlebotomus species and 5 Sergentomyia species; polymerase chain reaction for leishmanial DNA was negative. This assessment suggests that endemic visceral leishmaniasis transmission has occurred in diverse locations in Bhutan. Surveillance, case investigations, and further parasite, vector, and reservoir studies are needed. The potential protective impact of bed nets should be evaluated.This assessment was made thanks to the support that the Spanish Agency for International Cooperation for Development (AECID) provides to WHO for the control of visceral leishmaniasis. We are grateful to Rinzin Namgay from the Ministry of Health, Bhutan and the staff from Karuna House canine shelter in Trashigang, Bhutan, for their support during the field study

Evaluating Rural Electrification: Illustrating Research Gaps with the Case of Bhutan

Electrification, especially rural electrification (RE), is a core component of the Sustainable Development Goals and a major focal point of the global development community. Despite this focus, more than one billion people worldwide do not have access to electricity, and electrification growth rates are not keeping pace with population growth. In this paper, we posit that lack of progress is partly driven by a misalignment between academic research and energy planners’ and policy makers’ needs. A majority of the studies measuring the impacts of electrification focus on precise estimation of a few outcomes, specifically health, education and productivity impacts. Other important impacts, e.g. environmental, have remained largely unstudied. As a consequence, quantifying the full set of costs and benefits of expanding electricity access is difficult and rarely done. When cost benefit analyses are done, they are often incomplete, and conclusions are highly susceptible to unavailable or uncertain parameter estimates. We illustrate these arguments in the case of Bhutan, where RE rates have expanded rapidly in the past few decades. We show that RE had positive impacts related to fuelwood consumption, education, and employment, but we do not find an effect on health. We then use these impact estimates to conduct cost-benefit analyses. Because there are more parameters in these calculations than we have data for from Bhutan, we transfer reasonable estimates from related contexts. However, to acknowledge the uncertainty induced by this process, we conduct Monte Carlo analyses to see if the NPV calculations are robust to alternative parameter values. Based on this exercise, we highlight research gaps that are preventing 1) thorough accounting of the net present value of RE in diverse settings and 2) financial investment in the sector.JEL Codes: O13, O2

Seismic response analyses and performance assessment of masonry-infilled reinforced concrete frame buildings in Bhutan without and with soft storey

Bhutan locates in a high seismicity region but has no seismic design code of its own. Recent devastating earthquake in Nepal, which is located in the same region as Bhutan and with similar construction types, raises the concern on the seismic safety of building structures in Bhutan. This study is aimed at assessing the performance of masonry-infilled and soft storey reinforced concrete frame buildings in Bhutan under the 475-and 2475-year return period ground motions predicted from the Probabilistic Seismic Hazard Analysis. A nonlinear strut model is used to model the infill wall, and the influence of openings and soil–structure interaction are considered in the analyses. The result suggests that the masonry-infilled reinforced concrete frame buildings in Bhutan could suffer repairable and irreparable damages under the 475-year return period ground motions and severe damages and even collapse under the 2475-year return period ground motion. The buildings with the soft storey are found to be more vulnerable than the normal masonry-infilled reinforced concrete buildings. The design recommendation of Indian Seismic Code improves the performance of soft storey buildings but cannot fully negate the soft storey effect. This study is the first such effort in assessing the performance of general building stocks in the high seismicity Bhutan. The results can guide the seismic strengthening options and can be used for further loss predictions for seismic preparedness of the country

Effect of partially infill wall on the seismic behavior of RC frame buildings

The partially infilled Reinforced Concrete (RC) frames have been one of the major victims of the earthquakes in the past. It is normally called as the captive column effect wherein the lower portion of the column is kept captive by the surrounding infill wall while the upper portion is allowed to deform laterally. The upper free portion of the column attracts huge shear force during earthquakes and might get severely damaged and possibly lead to the collapse of the buildings. Although there are a number of studies conducted on the masonry infilled RC frames in general, yet partially infilled frames have not been adequately studied under the dynamic load. In this study, a three storey RC building with partially infill wall on the ground floor is studied under the ground motions with the 475 year return period. The height of the infill wall is varied along the height of the columns and the resulting shear demands are estimated. To study the mitigation measures of the captive column effect, the shear and moment capacities of the ground floor columns are increased by factors of 2.5 and 4 times the original design strength. It was found that the captive column effect is maximum when the infill wall height is 75% of the column clear height. Increasing the shear strength of the column is found to be beneficial but providing the infill wall up to the full height of the column to eliminate the short-column effect is still the most desirable for structure protection

Tiger reappearance in Bhutan's Bumdeling Wildlife Sanctuary: a case for maintaining effective corridors and metapopulations

The tiger Panthera tigris is globally 'Endangered'(Goodrich et al., 2015). The Himalayan Kingdom of Bhutan is an important stronghold (Tempa et al., 2019) for this ecologically and economically important apex predator (Estes et al., 2011; Thinley et al., 2018). Here, we report the reappearance of the tiger in Bumdeling Wildlife Sanctuary (BWS) in north-eastern Bhutan (Fig. 1a), after a likely absence of 12 years

Drift demand predictions in low to moderate seismicity regions

This paper presents results obtained from a recent study which is aimed at assessing the drift demand on buildings of different height ranges for projected earthquake scenarios in Australia. Parametric studies of tall buildings have been carried out based on modal analysis. Important parameters defining the response behaviour of buildings including building height, structural configurations and form of construction have been collated from recent field survey reports. The estimated drift demands can be compared with the limiting drift capacity to enable various levels of damage to be predicted for given earthquake scenarios, building types and site classes