Earthquake Risk in Nepal: Strategies for Pre-Disaster Preparedness

Abstract: Nepal ranks among the most earthquake-vulnerable countries globally due to the active collision between the Indian and Eurasian tectonic plates. This paper examines Nepal’s seismic risk, focusing on structural vulnerability, historical earthquakes, and policy interventions. Recommendations include resilient construction, retrofitting existing infrastructure, mitigation of non-structural hazards, and capacity building. The study aligns with the National Building Code (NBC-105), IS 1893, and Eurocode 8 provisions for seismic design.

1.Introduction

Nepal’s seismic vulnerability stems from its location along the Main Himalayan Thrust (MHT), resulting from the subduction of the Indian plate beneath the Eurasian plate. The 2015 Gorkha earthquake (Mw 7.8) underscored structural weaknesses and catalyzed revisions in seismic design codes, including the NBC-105 (2020). Civil engineering strategies must incorporate these codes to reduce risk and enhance resilience.

2. Seismic Risk

Seismic Risk Context Western Nepal presents a major seismic gap. Historical data shows that the region between Gorkha (Nepal) and Dehradun (India) has not experienced a major earthquake for over 518 years, indicating high strain accumulation. Rural structures and urban non-compliant buildings exacerbate potential damage.

3. Historical Earthquakes Major earthquakes in Nepal include:

v  1255 AD – Kathmandu Valley

v  1833 AD – Central Nepal (Mw ~7.7)

v  1934 AD – Bihar–Nepal (Mw 8.0–8.4)

v  2015 AD – Gorkha (Mw 7.8)

Global comparisons include Chile (1960, Mw 9.5) and Japan (2011, Mw 9.0). Historical data highlights the necessity for both structural and non-structural mitigation.

4.Causes and Effects of Earthquakes

 4.1 Causes

v  Tectonic (plate collisions, thrust faults)

v  Volcanic

v  Induced (human activities: mining, reservoirs)

4.2 Effects - Structural collapse - Non-structural damage (furniture, water tanks) - Secondary hazards: landslides, fires, tsunamis

5.Engineering Strategies

v  Resilient Construction Seismic-resistant design increases construction costs by only 5–7% for traditional materials, significantly improving safety.

v  Retrofitting Existing Structures Retrofitting public buildings costs approximately 30% of new construction, enhancing durability and life safety.

v  Mitigation of Non-Structural Hazards Securing furniture, utilities, and decorative items reduces 50% of earthquake-related injuries.

6. Policy and Preparedness Measures

6.1 Assessment and Classification

v  Visual Risk Assessment (VRA)

v  Red, Yellow, Green zoning

6.2 Policy and Enforcement - Extend building permits and inspections to rural areas - Promote lightweight timber construction

6.3 Hazard Mapping - Identify landslide, flood, fire-prone areas - Implement clear emergency evacuation routes

6.4 Education and Capacity Building - Public awareness programs - Standardized emergency drills - Technical training for construction workforce

7. Alignment with Standards

v  NBC-105 (2020): Seismic design requirements

v  IS 1893: Criteria for earthquake-resistant structures in India/Nepal context

v  Eurocode 8: European seismic design guidance for structures

8. Conclusion Earthquakes cannot be predicted, but their impact can be minimized through pre-disaster preparedness. Adoption of resilient construction, retrofitting, non-structural hazard mitigation, and capacity building are essential. Compliance with NBC-105, IS 1893, and Eurocode 8 ensures structural safety and sustainable risk reduction in Nepal.