Earthquake risk zones and their distribution in India

India faces significant earthquake risks due to its geographical location and tectonic activity. A large portion of the country is prone to seismic events, with risk levels varying across different regions.

Distribution of risk zones across India

• Zone V (very high risk) - Includes the northern Himalayan region, the northeastern part of the country, and the Andaman and Nicobar Islands. These areas are most susceptible to severe earthquakes.
• Zone IV (high risk) - Covers areas adjacent to the very high-risk zones, often including major cities that are vulnerable to significant seismic activity.
• Zone III (moderate risk) - Encompasses parts of central India, where the risk is lower but still notable.
• Zone II (low risk) - Predominantly the central and southern peninsula, where earthquake occurrences are less frequent and less intense.

Many of India's largest cities are located in Zones IV and V, increasing the potential for widespread damage and loss of life during seismic events.

Causes of earthquakes in India

The frequent earthquakes in India are primarily driven by tectonic movements involving major continental plates. Understanding these causes is crucial for assessing risk and planning mitigation strategies.

Tectonic activity driving seismic events

• Plate movement - The primary cause of earthquakes in India is the movement of the Indo-Australian plate towards the Eurasian plate. This convergence happens at a rate of approximately 40 mm per year, creating immense pressure along fault lines.
• High-magnitude events - The northeastern region of India has a history of experiencing earthquakes with magnitudes of 8.0 or higher, largely due to this tectonic interaction in the Himalayan belt.

Challenges of earthquake preparation in India

India faces unique obstacles in preparing for earthquakes due to its vast size, dense population, and varying levels of infrastructure development. These factors complicate efforts to mitigate risks effectively.

Key obstacles in earthquake readiness

• Extensive risk area - Approximately half of India's land area is prone to damaging earthquakes, making comprehensive preparation a daunting task.
• Population density - With a population of around 1.5 billion and an average density of 420 persons per km², the potential impact on human life and property is enormous, especially in urban centres.
• Infrastructure vulnerability - Many existing buildings, particularly in high-risk zones, do not meet modern earthquake resistance standards, increasing the likelihood of structural failure during seismic events.
• Resource constraints - Implementing widespread safety measures across such a large and diverse country requires significant financial and logistical resources, which are often limited.

Strategies for earthquake preparedness and retrofitting

In response to the significant seismic risks, India has developed various strategies to enhance preparedness and reduce the impact of earthquakes. These efforts focus on both immediate response capabilities and long-term structural improvements.

National initiatives for earthquake mitigation

• National Disaster Management Authority (NDMA) - Established to coordinate disaster preparedness and response efforts across the country, ensuring a structured approach to managing earthquake risks.
• National Disaster Response Force (NDRF) - A specialised team trained to handle emergency situations, including search and rescue operations following earthquakes.

Seismic retrofitting

Seismic retrofitting is a key strategy involving the modification of existing buildings to meet current earthquake resistance standards. Priority is given to critical infrastructure such as hospitals and schools, though residential blocks of flats are also considered.

Challenges with retrofitting:

• High costs, even with available loans.
• Lack of official oversight to ensure buildings are upgraded to the required standards.
• This leaves millions of homes unsafe.

Global earthquake trends and their impact

Earthquakes are a global hazard with varying frequency and destructive power. Understanding worldwide patterns provides context for India's challenges and highlights the unpredictable nature of these events.

Patterns and characteristics of global seismic activity

• Annual variation - The number of earthquakes worldwide fluctuates each year, with a significant majority falling in the lower magnitude range of 5.0 to 5.9. Fewer events occur in the higher ranges of 6.0 to 6.9 and 7.0 to 7.9.
• Long-term trend - Despite yearly variations, there is no significant change in the overall frequency of earthquakes over time, indicating that seismic activity remains a consistent threat.
• Unpredictability and reach - Unlike other natural hazards such as volcanoes or tropical cyclones, earthquakes occur in more regions globally and cannot be predicted, making them particularly hazardous.
• Destructive power - High-magnitude earthquakes possess immense destructive potential, often surpassing other natural hazards in terms of impact and fatalities, as seen in events like the 2016 Nepal earthquake which served as a wake-up call for India.