Spatial Landslide Risk Assessment at Phuentsholing, Bhutan

Dikshit, Abhirup; Sarkar, Raju; Pradhan, Biswajeet; Acharya, Saroj; Alamri, Abdullah

doi:10.3390/geosciences10040131

Cited by 50 publications

(36 citation statements)

References 44 publications

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“…Although the Nepal region saw a major earthquake in 2015, such a disastrous event in Bhutan has not occurred in the last century owing to variations in the segments of the Himalayas. These segments of Himalaya have divergent topography, geology and earthquake patterns [2]. There is a widespread belief that major earthquakes would not strike in Bhutan; however, it was reported that a major earthquake greater than a magnitude of 8 occurred in May 1713 which left in its wake widespread infrastructural damage and a staggering loss of human life.…”

Section: Introductionmentioning

confidence: 99%

Parametric Study of Local Site Response for Bedrock Ground Motion to Earthquake in Phuentsholing, Bhutan

et al. 2020

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Earthquakes, when it comes to natural calamities, are characteristically devastating and pose serious threats to buildings in urban areas. Out of multiple seismic regions in the Himalayas, Bhutan Himalaya is one that reigns prominent. Bhutan has seen several moderate-sized earthquakes in the past century and various recent works show that a major earthquake like the 2015 Nepal earthquake is impending. The southwestern city of Bhutan, Phuentsholing is one of the most populated regions in the country and the present study aims to explore the area using geophysical methods (Multispectral Analysis of Surface Waves (MASW)) for understanding possibilities pertaining to infrastructural development. The work involved a geophysical study on eight different sites in the study region which fall under the local area plan of Phuentsholing City. The geophysical study helps to discern shear wave velocity which indicates the soil profile of a region along with possible seismic hazard during an earthquake event, essential for understanding the withstanding power of the infrastructure foundation. The acquired shear wave velocity by MASW indicates visco-elastic soil profile down to a depth of 22.2 m, and it ranged from 350 to 600 m/s. A site response analysis to understand the correlation of bedrock rigidness to the corresponding depth was conducted using EERA (Equivalent-linear Earthquake Site Response Analysis) software. The amplification factors are presented for each site and maximum amplification factors are highlighted. These results have led to a clear indication of how the bedrock characteristics influence the surface ground motion parameters for the corresponding structure period. The results infer that the future constructional activity in the city should not be limited to two- to five-story buildings as per present practice. Apart from it, a parametric study was initiated to uncover whatever effects rigid bedrock has upon hazard parameters for various depths of soil profile up to 30 m, 40 m, 60 m, 80 m, 100 m, 120 m, 140 m, 160 m, 180 m and 200 m from the ground surface. The overriding purpose of doing said parametric study is centered upon helping the stack holders who can use the data for future development. Such a study is the first of its kind for the Bhutan region, which suffers from the unavailability of national seismic code, and this is a preliminary step towards achieving it.

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Section: Introductionmentioning

confidence: 99%

Parametric Study of Local Site Response for Bedrock Ground Motion to Earthquake in Phuentsholing, Bhutan

et al. 2020

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“…the Langtang Valley (Jones et al, 2019). Although forest coverage of >60% is prescribed by the Bhutanese constitution, and most of the outcropping rocks are harder rocks of the Greater Himalayan Series, there are areas of weaker geology where landslides are a serious risk (Dikshit et al, 2020). In Bhutan this is highly critical as the road network resembles a fishbone with very few, to no alternative routes from the main east-west highway, and helicopter landing spots are scarce.…”

Section: Discussionmentioning

confidence: 99%

Seismic hazard and risk in Bhutan

et al. 2020

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We present the first modern seismic hazard and risk assessment in the Bhutan Himalaya. We used a fault-based probabilistic seismic hazard analysis based on fault locations, slip-rates and paleoseismic earthquake data. We worked with two seismic intensity measures: the peak-ground acceleration (PGA) and Modified Mercalli Intensity (MMI). We extend the hazard analysis to risk by using local building distribution data and making various assumptions about building distribution and fragility. We find, unsurprisingly, that the Main Himalayan Thrust (MHT) is the primary source of hazard, with oblique strike-slip faults cutting across and beneath the Himalaya, and extensional grabens on the northern edge of Bhutan a secondary hazard. The hazard is highest in the southern part of Bhutan where the MHT is shallow, and site conditions lead to amplification of shaking. The risk does not reflect the hazard solely, but also the distribution of exposure, which is concentrated in the cities. We also simulated the 1714 MW8 earthquake, producing 10,000 possible shakemaps in terms of PGA and MMI; we find that many locations could experience PGA values of over 1 g, and on average, up to 18% of the Bhutanese population could be affected. Refining the probable frequency of larger events on the MHT in this region, developing local Ground Motion Prediction Equations, creating tailored vulnerability models for typical Bhutanese buildings, and improving the exposure mapping would most improve the hazard and risk results shown here. The existing building code of Bhutan, adopted from the Indian Seismic Zonation of 2002 (BIS-1893, 2002), uses a PGA of 0.36 g uniformly applied across the entire country. Our study, however, presents a non-uniform hazard level across the country and thus questions the relevancy of the current code of construction practices in the country.

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“…In the geological parameters, we divide by formation using porosity, sorting, mineral content, and density of joints considerations. Vegetation parameters are classified based on the presence of vegetation (Dikshit et al, 2020). Slope and Elevation is classified into 5 classes from <15 to > 45 for slope (Bijukchhen et al, 2012); and <0 to >1000 for elevation (Chen et al, 2014).…”

Section: Landslide Hazard Assessmentmentioning

confidence: 99%

“…After that, we use the WLC method using these 4 parameters to make a Landslide Vulnerability Assessment Map (Figure 7.). Vulnerability map is divided into five classes: Very Low (0-0.36), Low (0.37-0.48), Moderate (0.49-0.64), High (0.65-0.76), and Very High (0.77-1) (Dikshit et al, 2020). The maps derived using both the components resulted in the Vulnerability map.…”

Section: Landslide Vulnerability Assessmentmentioning

confidence: 99%

Landslide Disaster Potential Mapping in Feasibility Study of Walini Areaas the Candidate for the Capital City of West Java

Putra¹,

I.G.M.²,

Rahman³

et al. 2021

Proceedings of the 5th International Conference of Geological Engineering Faculty

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Walini, Cikalongwetan District, West Bandung Regency is one of the 3 plans for the relocation of the capital city of West Java. This area is also projected to become a high-speed train station from Bandung City to Jakarta. This paper is aimed to reveal the feasibility of the Walini area based on landslide potentials. The methodology of this research is the Weighted Linear Combination (WLC) method using the parameters of Landslide Hazard Assessment parameters (rainfall, geology, slope, elevation, vegetation) and Landslide Vulnerability Assessment parameters (population, LULC, proximity to the road, proximity to stream). The results show that this area has 5 classes of risk, from Very Low to Very High. Kanangasari Village is filled by Moderate to Very High Class but the dominant class is High with an area 8,179 km 2 (68,01% of the area). Mandalasari and Mandalamukti are in High to Very High Class. Very High Class in Mandalamukti is 4,959 km 2 (86,5% of the area). Meanwhile, Mandalasari has 7,906 km 2 (62,7% of the area) of Very High Class. It can be concluded that the Walini area is less suitable as a candidate for the capital city of West Java and the High-Speed train station based on landslide disaster because the potential risk of Very High class is up to 50 % and High class is 40% of the total area.

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Spatial Landslide Risk Assessment at Phuentsholing, Bhutan

Cited by 50 publications

References 44 publications

Parametric Study of Local Site Response for Bedrock Ground Motion to Earthquake in Phuentsholing, Bhutan

Parametric Study of Local Site Response for Bedrock Ground Motion to Earthquake in Phuentsholing, Bhutan

Seismic hazard and risk in Bhutan

Landslide Disaster Potential Mapping in Feasibility Study of Walini Areaas the Candidate for the Capital City of West Java

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