Uttarkashi Earthquake Swarm

The Uttarkashi district in Uttarakhand, has recently experienced a series of small earthquakes. From January 24 to 25, 2025, nine tremors occurred within six days. These tremors, with magnitudes between 2 and 3 on the Richter scale, caused panic among local residents. Although mild, these earthquakes have raised concerns about the potential for a larger seismic event in the region.

Earthquake Swarms

• An earthquake swarm consists of a sequence of small earthquakes that occur in a specific area over a short period without a single large quake, known as the mainshock.
• Unlike typical earthquakes where a mainshock is followed by aftershocks, swarms can show no clear pattern.
• Their activity may even increase rather than diminish over time.

Geological Context

• Uttarkashi lies in Zone IV of India’s seismic map, indicating a high likelihood of earthquakes.
• The region has not experienced earthquake since 1991, which resulted in over 700 fatalities.
• The underlying geological processes involve the collision of the Indian and Eurasian tectonic plates, which move at a rate of 50-52 mm per year.
• This constant movement creates stress and leads to cracks in the Earth’s crust.

Potential Risks

Seismologists warn that the current swarm of small earthquakes could indicate that a larger earthquake is imminent. While these minor tremors may relieve some built-up energy, they do not eliminate the risk of a major quake. Experts believe that the frequent seismic activity could serve as a warning against excessive human intervention in these geologically active regions.

Historical Context

Historically, Uttarkashi has faced severe seismic events. The last major earthquake in 1991 was devastating. The region’s geological history suggests a pattern of quakes followed by periods of relative calm. This historical context raises concerns about the possibility of another major earthquake occurring soon.

Monitoring and Preparedness

Continuous monitoring of seismic activity is crucial in earthquake-prone areas like Uttarkashi. Local authorities and scientists are urged to develop preparedness strategies. Public awareness campaigns can educate residents about safety measures during earthquakes.

Questions for UPSC:

1. Discuss the geological factors contributing to earthquake swarms in Uttarkashi.
2. Critically examine the impact of human activities on seismic zones and potential earthquake risks.
3. Explain the significance of monitoring seismic activity in earthquake-prone regions like Uttarkashi.
4. With suitable examples, discuss the historical patterns of seismic activity in the Himalayas.

Answer Hints:

1. Discuss the geological factors contributing to earthquake swarms in Uttarkashi.

1. The collision of the Indian and Eurasian tectonic plates generates stress in the Earth’s crust.
2. Uttarkashi lies in Zone IV of India’s seismic map, indicating high earthquake susceptibility.
3. The region has not experienced a major quake since 1991, leading to energy accumulation.
4. Small earthquakes (magnitude 2-3) can indicate stress release but do not eliminate major quake risks.
5. Earthquake swarms occur without a mainshock, showing irregular patterns of seismic activity.

2. Critically examine the impact of human activities on seismic zones and potential earthquake risks.

1. Human interventions, such as construction and mining, can destabilize geological formations.
2. Excessive land use in seismically active areas may increase vulnerability to earthquakes.
3. Urbanization can lead to increased population density, raising risks during seismic events.
4. Infrastructure may not be designed to withstand major earthquakes, amplifying potential damages.
5. Awareness and regulations are crucial to mitigate risks associated with human activities in these zones.

3. Explain the significance of monitoring seismic activity in earthquake-prone regions like Uttarkashi.

1. Monitoring helps in early detection of seismic events, allowing timely warnings to residents.
2. Data collection aids in understanding local geological conditions and predicting future quakes.
3. Continuous observation can identify patterns in earthquake swarms, informing risk assessments.
4. Preparedness strategies can be developed based on monitoring data to enhance community safety.
5. Public awareness campaigns can educate residents on safety measures and response actions during quakes.

4. With suitable examples, discuss the historical patterns of seismic activity in the Himalayas.

1. The 1991 Uttarkashi earthquake resulted in over 700 fatalities, marking historical event.
2. Historical records show a cycle of major quakes followed by periods of relative calm in the region.
3. Earthquake activity in the Himalayas has been linked to tectonic plate movements over centuries.
4. Regions like Nepal and Bhutan also exhibit similar seismic patterns, denoting a broader trend.
5. About historical patterns aids in predicting future seismic risks and preparing accordingly.