Earthquake

Context: Almost 2,200 earthquakes were recorded in the area around Iceland’s capital Reykjavik in the past 24 hours.

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• Iceland is Europe’s biggest and most active volcanic region.
• The North Atlantic Island straddles the Mid-Atlantic Ridge- separating the Eurasian and North American tectonic plates.
• The recent tremors have been said to be from beneath Mount Fagradalsfjall.

About Earthquakes

• An earthquake is a sudden release of energy in the Earth’s crust that creates seismic waves.
• Key terms related to earthquakes:
  • Focus: The focus, also known as the hypocentre, is the point within the Earth where an earthquake originates.
  • Epicenter: The point on the Earth’s surface directly above the focus or source of an earthquake.
  • Aftershocks: Smaller earthquakes that occur after a larger earthquake, as the Earth adjusts to the sudden movement.
  • Seismic waves: The waves of energy that travel through the Earth’s crust and cause ground shaking during an earthquake.

• Causes of Earthquakes:
  • Plate tectonics: The movement of the Earth’s tectonic plates can cause earthquakes when the plates interact along plate boundaries.
  • Volcanic activity: Earthquakes can occur when magma moves beneath a volcano, causing the ground to shake.
  • Human activity: Human activities, such as the injection of fluid into the ground for waste disposal, or the extraction of oil and gas from underground reservoirs, can induce earthquakes.
  • Reservoir-induced earthquakes: The filling or emptying of large reservoirs, such as lakes or dams, can cause earthquakes as the weight of the water changes and affects the Earth’s crust.
  • Glacial rebound: The movement of glaciers can cause earthquakes as they advance or retreat and cause changes in the Earth’s crust.
• Measurement of earthquakes: The magnitude and intensity of an earthquake are two ways to measure its size and impact.
  • Magnitude: The magnitude of an earthquake is a measure of its energy release, and is determined from measurements of the seismic waves generated by the earthquake.
    • The most commonly used scale for measuring earthquake magnitude is the Richter scale, which was developed in the 1930s.
    • The Richter scale ranges from 0 to 9, with each increase in magnitude representing a tenfold increase in energy release.
  • Intensity: The intensity of an earthquake is a measure of its impact at a specific location, and is determined by the effects of the seismic waves on the ground, buildings, and people.
    • The most commonly used scale for measuring earthquake intensity is the Modified Mercalli Intensity (MMI) scale, which ranges from I to XII.
    • The MMI scale takes into account factors such as the type of building construction, the height of the building, and the distance from the earthquake’s epicenter.
• Seismic waves: Seismic waves are waves of energy that travel through the Earth’s crust and cause the ground to shake during an earthquake.

India’s Earthquake Propensity

India’s large and increasing population coupled with unsustainable construction and planning that include multi-storeyed buildings and skyscrapers, keep India at high earthquake risk.

• Over the past 2 decades, the country has experienced 10 major earthquakes that have resulted in over 20,000 deaths.
• As per the current seismic zone map of the country, over 59% of India’s land area is under threat of moderate to severe seismic hazard.
  • The entire Himalayan belt is considered prone to hazardous earthquakes of magnitude exceeding 8.0.
    • Example: 1897 Shillong Earthquake (M8.7); 1905 Kangra (M8.0); 1950 Assam-Tibet earthquake etc (M8.6).
  • Himalayas is the region of convergence of Indian and Eurasian plates.
    • The Indian plate is moving at a speed of one centimetre per year towards the north and northeastern direction.
• In the recent past, the inter-plate boundary areas have also been experiencing devastating earthquakes, although the magnitude is lesser than the Himalayan earthquakes.
  • The Andaman and Nicobar Islands are situated on an inter-plate boundary and frequently experience damaging earthquakes.
• The North-Eastern part of the country continues to experience moderate to large earthquakes at frequent intervals.
  • On an average, the region experiences an earthquake with a magnitude greater than 6.0 every year.

Earthquake Zones of India

India is divided into four earthquake zones (Zone II-Zone V).

• There was a change in the earthquake map of India where Very low risk zone and Low risk zone were merged into single ‘low risk zone’.
• Zone IV and Zone V have experienced some of the most devastating earthquakes in India.
  • These include North-east states, areas to the north of Darbhanga and Araria along the Indo-Nepal border in Bihar, Uttaranchal, Western Himachal Pradesh (around Dharamshala) and Kashmir Valley in the Himalayan region and the Kuchchh region of Gujarat.
  • Most of the areas that are safe are from the stable landmass covered under the Deccan plateau.

Impact of Earthquakes

• Damage to life and property: Earthquakes of high magnitude cause total collapse of the entire structure/building. This is accompanied by disruption of underground pipelines and railway lines, collapse of dams which cause sudden floods that in turn endanger life and livelihood.
• Changes in river courses: Sometimes river channels are blocked or their courses are changed due to the impact of earthquake.
• Tsunami and other associated disasters: Earthquakes cause Tsunamis which disrupts live in settlements of coastal areas. It sinks large ships. Example: Tsunami in Indonesia Tsunami near Sumatra coast had cost properties worth billions of rupee.
• Landslides and avalanches are also caused by Earthquakes.

Earthquake Hazard Mitigation

• Establishing earthquake monitoring centres (seismological centres) for regular monitoring and fast dissemination of information among the people in the vulnerable areas.
• Preparing a vulnerability map of the country and dissemination of vulnerability risk information among the people and educating them about the ways and means to minimise the adverse impacts of disasters.
• Community preparedness: Community preparedness like ‘DROP, COVER and HOLD’ technique in case of earthquakes.
• Planning: The Bureau of Indian Standards has published building codes and guidelines for safe construction of buildings against earthquakes. All infrastructure both the already existing ones and the upcoming ones needs to be upgraded by retrofitting techniques.
• Public education is educating the public on causes and characteristics of an earthquake and preparedness measures that can be created through sensitization and training programme for community, architects, engineers, builders, masons, teachers, government functionaries teachers and students.
• Engineered structures: Buildings need to be designed and constructed as per the soil strength and building structures on soft soil should be avoided as they are more likely to get damaged even if the magnitude of the earthquake is not strong.
  • Similar problems persist in the buildings constructed on the river banks which have alluvial soil.
• Strengthening the Preparedness Phase Urban Planning and Zoning -There is a need to enhance the efforts for integrating disaster risk reduction elements in settlement planning and land use zoning to mitigate flood and earthquake risks. Planned urban settlements and housing is the need of the day for disaster risk management that leads to sustainable development, particularly in ecologically sensitive regions, high risk locations and high population density pockets.

Initiatives taken by the Government for Earthquake Risk reduction and Mitigation:

1. National Earthquake Risk Mitigation Project (NERMP): The proposed project aims at strengthening the structural and non-structural earthquake mitigation efforts and reducing the vulnerability in the high-risk districts prone to earthquakes. The proposed components of the project include techno-legal regime, institutional strengthening, capacity building and public awareness etc.
2. National Building Code (NBC): The National Building Code of India (NBC), a comprehensive building code, is a national instrument providing guidelines for regulating the building construction activities across the country. The salient features of the revised NBC include meeting the challenges posed by natural calamities and reflecting the state-of-the-art and contemporary applicable international practices.
3. Efforts by Building Materials & Technology Promotion Council (BMTPC): The BMTPC has undertaken projects for retrofitting of life-line structures for generating awareness among the people as well as various government agencies about the need and techniques of retrofitting. The Council has initiated retrofitting of MCD school buildings in Delhi.
4. Initiative by Ministry of Panchayati Raj: It releases funds under Backward Regions Grant Fund (BRGF) for meeting critical infrastructural gaps and other developmental requirements. The ministry has financed several district plans under the BRGF for construction of panchayat buildings, anganwadi centres, school buildings, classrooms, roads, bridges, culverts etc.
5. Disaster Management Support (DMS) of ISRO: This programme provides timely support and services from aero-space systems, both imaging and communications, towards efficient management of disasters in the country. The DMS programme addresses disasters such as flood, cyclone, drought, forest fire, landslide and Earthquake. These include:

• creation of digital data base for facilitating hazard zonation, damage assessment etc.,
• monitoring of major natural disasters using satellite and aerial data
• development of appropriate techniques and tools for decision support
• establishing satellite based reliable communication network.
• deployment of emergency communication equipments and
• R&D towards early warning of disasters.

6. Indian National Centre for Oceanic Information System (INCOIS): It gives information to all responders about the origin, time, location of the epicentre, magnitude and depth of an earthquake inside the ocean and accordingly issues bulletins.

• Tsunami Early Warning System (TEWS) at INCOIS is capable of detecting all earthquake events of more than 6 Magnitude occurring in the Indian Ocean in less than 20 minutes of occurrence and first report on the occurrence of an earthquake in India and the Indian Ocean region is sent to MHA within 25-30 minutes indicating the location and magnitude of the earthquake.

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