the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Integrated Seismic Risk Assessment in Nepal
- Department of Civil Engineering, Pulchowk Campus, Lalitpur, Nepal
- Department of Civil Engineering, Pulchowk Campus, Lalitpur, Nepal
Abstract. As Nepal is at high risk of earthquakes, the district-wide (VDC/Municipality level) study has been performed for vulnerability assessment of seismic-hazard, and the hazard-risk study is incorporated with social conditions as it has become a crucial issue in recent years. There is an interrelationship between hazards, physical risk, and the social characteristics of populations which are significant for policy-makers and individuals. Mapping the spatial variability of average annual loss (seismic risk) and social vulnerability discretely does not reflect the true nature of parameters contributing to the earthquake risk, so when the integrated risk is mapped, such combined spatial distribution becomes more evident. The purpose of this paper is to compute the risk analysis from the exposure model of the country using OpenQuake and then integrate the results with socio-economic parameters. The methodology of seismic-risk assessment and the way of combining the results of the physical risk and socio-economic data to develop an integrated vulnerability score of the regions has been described. This study considers all 75 districts and corresponding VDC/Municipalities using the available census. The combined vulnerability score has been developed and presented by integrating earthquake risk and social vulnerability aspects of the country and represented in form of the map produced using ArcGIS 10. The knowledge and information of the relationship between earthquake hazards and the demographic characteristics of the population in the vulnerable area are imperative to mitigate the local impact of earthquakes. Therefore, we utilize social vulnerability study as part of a comprehensive risk management framework to recuperate and recover from natural disasters.
Sanish Bhochhibhoya and Roisha Maharjan
Status: final response (author comments only)
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RC1: 'Comment on nhess-2021-354', Anonymous Referee #1, 25 Jan 2022
The deveopment of a Social Vulnerability Index is a worthwhile advance in Nepal seismic risk assessment. While this is welcome, a serious omission in this paper is the absence of a detailed casualty analysis. In the conclusions, it is stated that, 'The authors are aware to the fact that numerous estimations such as casualties, non-structural damage, business-interruption loss and loss to critical infrastructure may improve the indicator of physical risk'.
The only information on deaths is in Table 1, which gives a poor indication on fatality risk. For example, had the Gorkha earthquake not occurred on a Saturday, there would have been a tragic loss of life in Nepalese schools, where many thousand classrooms were wrecked. All tabulations of death statistics need to be subject to counterfactual risk analysis (see www.llloyds.com).
At the very least, there should be a section of the paper addressing casualty risk. The authors note that the most recent Nepal census was in 2021. Ideally, this paper should be withheld for a number of months until it can incorporate this latest important demographic data.
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AC1: 'Reply on RC1', Roisha Maharjan, 26 Jan 2022
Thank you very much for the comment. We hope the following description addresses your comments:
1. Casualty risk analysis:
• Our study is inspired by the theoretical concept designed by Cutter (1996) and Cardona (2005). Basically, the idea is to combine the components of natural hazards threat (seismic hazard), potential economic losses (seismic risk), and social vulnerability by binding them to particular places.
• The main objective of our study is to compute probabilistic risk analysis (physical risk) from the exposure model and physical vulnerability model (probability of loss at a given intensity level) of the country and then integrate the results with the socio-economic parameters. The average annual loss is taken as physical risk, as done in the studies of Burton and Silva1; and Chaulagain2 (for Nepal). Hence, just as in those studies, all other estimations like casualties, non-structural damage, business interruption is assumed as proportional to that of building damage cost.
• We agree that the detailed casualty analysis might improve the hazard analysis, but this study is primarily focused on combining seismic-physical risk and social vulnerability i.e., integrated risk analysis (seismic hazard aggravated by social factor).
• In the conclusions, it is stated that 'The authors are aware of the fact that numerous estimations such as casualties, non-structural damage, business-interruption loss and loss to critical infrastructure may improve the indicator of physical risk'. However, only economic losses to buildings are utilized at this stage as an initiation for integrated seismic risk analysis in Nepal. (line 374-375).
• Table 1 in the paper has been presented to demonstrate the death numbers as a result of historical seismic events as a part of the literature review.
2. Counterfactual risk analysis:
• We hope that the future seismic hazard and risk analysis involve the counterfactual risk analysis. “If the shaking in 2015 had been some other day, the repercussions would have been more intense.” Such counterfactuals are based on experts’ hypotheses and convenience3. However, our procedure to assess the hazard curve and seismic losses is a completely probabilistic approach void of such counterfactuals. As previously mentioned, our main focus is to calculate integrated earthquake risk for Nepal. So, for physical risk, we have quantified the casualty in terms of estimated losses for a collection of assets within the seismic risk analysis.
3. Census:
• The detailed report of Census 20014 was published in December 2003 (two years after the census). In the case of Census 2011, the national report5 was published in November 2012 (one year after the census), while its detailed monograph6,7 was published in December 2014 (three years after the census). Now for the 2021 census, delayed due to the COVID pandemic, the census survey that was supposed to be conducted in early 2021 was delayed to late December. A rough estimate of total populations has been announced as January 24, but a detailed report and data availability might take a year or more, just like the previous two censuses. However, we really hope that the detailed report will be made available soon so that an advanced study integrating every possible uncertainty and requirement can be conducted.1 Burton, C.G., Silva, V., 2016. Assessing integrated earthquake risk in OpenQuake with an application to Mainland Portugal. Earthquake Spectra 32, 1383–1403.
2 Chaulagain, H., Rodrigues, H., Silva, V., Spacone, E., Varum, H., 2015. Seismic risk assessment and hazard mapping in Nepal. Natural Hazards 78, 583–602.
3 King G, Zeng L. The dangers of extreme counterfactuals. Political analysis. 2006;14(2):131-59.
4 Central Bureau of Statistic (CBS), 2003. Population Monograph of Nepal
5 Central Bureau of Statistic (CBS), 2012. National Population and Housing Census 2011 (National Report).
6 Central Bureau of Statistic (CBS), 2014a. Population Monograph of Nepal Volume I (Population Dynamics).
7 Central Bureau of Statistic (CBS), 2014b. Population Monograph of Nepal Volume III (Economical Demography).
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AC1: 'Reply on RC1', Roisha Maharjan, 26 Jan 2022
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RC2: 'Comment on nhess-2021-354', Anonymous Referee #2, 02 Apr 2022
Dear Sanish Bhochhibhoya and Roisha Maharjan,
Dear Editor Prof. Dr. Heidi Kreibich,
Please find in the attachment the general, specific, and technical comments for this manuscript.
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AC2: 'Reply on RC2', Roisha Maharjan, 10 May 2022
Thank you very much for your extensive review of our paper including comments and suggestions. A major revision of the paper has been carried out to take account of all the comments. We believe that during the process, the paper has been significantly improved. We are more than grateful to receive such a detailed examination of our paper. We have sequentially addressed all of the points raised by the referee in each section of the paper. The attached document is the file addressing comments with all the details.
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AC2: 'Reply on RC2', Roisha Maharjan, 10 May 2022
Sanish Bhochhibhoya and Roisha Maharjan
Sanish Bhochhibhoya and Roisha Maharjan
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