Why the Himalayan system is an earthquake hotspot? How does an earthquake in Himalayas affect the great northern plains of India? Suggest suitable measures of mitigation.

(15     marks, 250 words)

Answer

Earthquakes are vibrations of the Earth caused by rupture and sudden movements of rocks that have been strained beyond their elastic limits. Earthquakes are caused by (i) rupture and sudden movements of rocks (folding and faulting), (ii) movement of plates (plate tectonics), (iii) volcanic eruptions, and (iv) anthropogenic factors. Earth’s internal and crustal movements are described by the Plate tectonic theory. The convective cells generated by the rising, spreading and sinking of molten material are the driving force for plate movements.


Quakes in Himalayas and the Nepal Earthquake of 2015:

The Himalayan region is one of the most seismically active in the world, but large earthquakes have occurred there infrequently. As Indian plate pushes against Eurasian plate, pressure is released in the form of earthquakes. Plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the Earth's crust and cause the shaking that we feel.

The quakes in this region are a manifestation of the ongoing convergence between the IndoAustralian and Asian tectonic plates that has progressively built the Himalayas over the last 50 million years. Nepal lies on the fault line and experiences the earthquake most frequently.


Effect of Earthquake on northern Indian plain:

1.     Liquefaction: Indian plain is mainly composed of alluvial soil. Liquefaction of soil causes structural instability in the earth quake affected area. Also, it may further aggravate the impacts of seismic waves causing loss of life and property.

2.     Down Stream Flooding: Earthquake triggers landslides and causes changes in river channels which may lead to breach in river water carrying capacity of Ganges river system.

3.     Heavy siltation and sedimentation: They will increase pressure on infrastructure like dams, barrages and irrigation systems. Such pressure during seismic events could further the effects of earthquake.

4.     Agriculture Livelihood: Inundation of fertile lands which will cause heavy economic distress to farmers.

5.     Food security: Considering the productivity and volume of food grain production in the region it will have severe impact on the food security of the nation.




Suitable measures of mitigation:

•        Preparation of disaster management (DM) plans at national, state and district level. And its effective implementation.

•        Training trainers in professional and technical institutions; training professionals like engineers, architects, and masons in earthquake-resistant construction.

•        Enforcing and monitoring compliance of earthquake-resistant building codes, town planning bye-laws and other safety regulations.

•        Developing an inventory of the existing built environment; assessing its seismic risk and vulnerability by carrying out a structural safety audit of all critical lifeline structures.

•        Increasing the awareness of earthquake risk and vulnerability and seismic risk reduction measures to various stakeholders through sensitisation workshops, seminars and public awareness campaigns.

•        Carrying out the vulnerability mapping of earthquake-prone areas and creating inventory of resources for effective response.

•        Setting up National Disaster Response Force (NDRF) and State Disaster Response Force (SDRF) battalions, training and equipping them.


Conclusion:

India’s high earthquake risk and vulnerability is evident from the fact that about 59 per cent of India’s land area could face moderate to severe earthquakes. Hence long-term and sustained efforts are required to address the problem of earthquake risk in India.