Earthquake

India faces significant earthquake risk, with about 59% of its land area susceptible to moderate to severe earthquakes. The country has experienced devastating earthquakes, highlighting the fragility of its built environment and inadequate preparedness. The causes include plate tectonics and human activities like underground nuclear explosions.India's earthquake-prone zones emphasize the need for adherence to building codes. Government efforts include the National Earthquake Risk Mitigation Project, NDMA guidelines, National Retrofit Program, and initiatives by BMTPC. Internationally, India is committed to disaster risk reduction through frameworks like Sendai and partnerships like CDRI.

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. The occurrence of several devastating earthquakes in areas hitherto considered safe from earthquakes indicates that the built environment in the country is extremely fragile and our ability to prepare ourselves and effectively respond to earthquakes is inadequate. Long-term and sustained efforts are required to address the problem of earthquake risk in India.

During the 1990s, throughout the International Decade for Natural Disaster Reduction (IDNDR) designated by the United Nations (UN), India experienced several earthquakes including the Uttarkashi quake of 1991, the Latur quake of 1993, the Jabalpur quake of 1997, and the Chamoli quake of 1999. These were succeeded by the Bhuj quake on January 26, 2001, and the Jammu & Kashmir quake on October 8, 2005. These seismic events highlighted that the majority of casualties resulted from building collapses. Conversely, in countries like the United States and Japan, earthquakes of similar intensity do not result in such extensive loss of life due to the implementation of structural mitigation measures and earthquake-resistant building features. This underscores the critical importance of enforcing strict adherence to town planning regulations and earthquake-resistant building codes in India.

• Plate Tectonics :It involves the movement of tectonic plates, which creates stress within the Earth's crust. This stress occurs through three main types of interactions: -
  1. Plates moving away from each other (Divergent),
  2. Plates pushing against each other (Convergent), and
  3. Plates sliding past each other sideways (Transform).
• At plate boundaries where these interactions occur, stress builds up and is released through slipping or rupturing known as 'faults.' When faults rupture, they produce seismic waves, which are vibrations that result in earthquakes
• Human activities like underground nuclear explosions and mine collapses have been observed to induce earthquakes.
• The buildup of pressure from storing large volumes of water behind dams, as seen in the case of the 1967 earthquake near the Koyna Dam in Maharashtra, can also trigger earthquakes.

Seismic waves are the waves generated during an earthquake.They are classified into following types:

• Body waves, named as such because they travel through the solid body of the Earth, consist of two types:
  • Primary( P-Waves):
    • Primary waves, also known as P-waves, are longitudinal waves similar to sound waves.
    • They have the ability to travel through solids, liquids, and gases.
    • P-waves are the fastest seismic waves and are the first to be recorded on a seismograph.
    • These waves are compressional or push-pull waves, causing materials to move forward and backward in the same direction as the waves themselves
  • Secondary (S-Waves):
    • S-waves can only travel through solids and are slower than primary waves.
    • These waves are shear waves because they move the material perpendicular to the direction of the wave
    • In other words , these are transverse waves similar to the light waves.
• Surface Waves: These waves travel along the surface or just below it. Two types are
  • Love Waves (L-Waves):
    • Love waves have a motion similar to S-waves, but individual particles of the material move only back and forth in a horizontal plane perpendicular to the direction of wave travel.
    • These waves are particularly damaging to building foundations.
    • Love wave is similar to movement of the snake on earth’s surface
  • Rayleigh Waves: These are similar to water waves, in that they move forward while causing individual particles of the material to move in an elliptical path within a vertical plane oriented in the direction of wave movement.

• Loss of life, injuries, displacement, and emotional distress
• Extensive damage to buildings, roads, bridges, and critical infrastructure
• Disruption of water supply, medical facilities, and transportation services
• Tsunamis causing widespread coastal destruction
• Volcanic eruptions releasing toxic gases, ashfall, and posing health hazards

In the last three decades, several significant earthquakes have occurred, each leaving a lasting impact:

Bhuj Earthquake (January 26, 2001):

• Magnitude: 7.7 on the Richter scale
• Location: Bhuj, Gujarat, India
• Death toll: Approximately 25,000
• Consequences: Extensive damage and devastation in Bhuj and surrounding areas.

Nepal-Sikkim Border Earthquake (September 18, 2011):

• Magnitude: 6.9
• Location: Near the Nepal-Sikkim border
• Death toll: More than 110 people
• Consequences: Significant damage to infrastructure and loss of lives.

Kashmir Earthquake (2005):

• Magnitude: 7.6
• Cause: Severe upthrust of the Indian plate against the Eurasian plate
• Consequences: Widespread destruction in Kashmir region, affecting both India and Pakistan.

World Level: Earth's major earthquakes occur mainly in belts coinciding with the margins of tectonic plates.

• The Circum-Pacific Belt,
  • The Circum-Pacific Belt affects coastal regions around the Pacific Ocean, including areas like New Zealand, New Guinea, Japan, the Aleutian Islands, Alaska, and the western coasts of North and South America.
  • The Circum-Pacific Belt, often termed the "Pacific Ring of Fire," accounts for about 75-80% of all earthquakes and 75% of all volcanoes
  • This belt features trenches such as the Kermadec Trench, Mariana Trench, and Tonga Trench.

• The Alpine Belt encompasses several major mountain ranges from west to east, including the Atlas Mountains, the Alps, the Caucasus Mountains, Alborz, Hindu Kush, Karakoram, and the Himalayas. It ranks as the second most seismically active region globally, following the Circum-Pacific Belt (the Ring of Fire), and accounts for 17% of the world's largest earthquakes

• In India, approximately 11% of the country falls under Zone V, around 18% in Zone IV, approximately 30% in Zone III, and the remaining in Zone II. This means that roughly 59% of India's landmass, covering all states, is susceptible to earthquakes of varying intensities.
• Zone V (very severe intensity zone): This zone encompasses entire northeastern India, some parts of Jammu and Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, the Rann of Kutch in Gujarat, some parts of North Bihar, and the Andaman & Nicobar Islands.
• Zone IV (severe intensity zone): This zone includes the remaining parts of Jammu & Kashmir, Ladakh, and Himachal Pradesh, the Union Territory of Delhi, Sikkim, northern parts of Uttar Pradesh, Bihar, and West Bengal, parts of Gujarat, small portions of Maharashtra near the west coast, and Rajasthan.
• Zone III (moderate intensity zone): This zone comprises Kerala, Goa, Lakshadweep islands, the remaining parts of Uttar Pradesh, Gujarat, and West Bengal, parts of Punjab, Rajasthan, Madhya Pradesh, Bihar, Jharkhand, Chhattisgarh, Maharashtra, Odisha, Andhra Pradesh, Tamil Nadu, and Karnataka.
• Zone II (low intensity zone): This zone covers the remaining parts of the country.

Earthquakes are measured either in terms of the magnitude or intensity of the shock.

• Modified Mercalli Scale = It measures Earthquake in terms of intensity which relates to damage an earthquake causes on the cultural landscape. It uses Roman numerals from I to XII to describe the intensity, with higher numbers indicating more severe effects . Intensity of Earthquake is measured by seismograph.
• Richter Scale - The Richter scale measures the magnitude of an earthquake, which represents the amount of energy released by the earthquake.It assigns a number to an Earthquake based on the severity of ground motion. It is a logarithmic scale and it is expressed in numbers 0 to 10.
• Moment Magnitude Scale - Geologists prefer the moment magnitude scale because it provides a more accurate measurement of an earthquake's magnitude. This scale considers various factors such as rupture area , displacement of rocks and geological properties of the area.(Whereas ,in richter scale the seismic waves used to measure the magnitude come from only a small part of the fault rupture and does not provide an accurate measure of total energy released)

The critical areas of concern for the management of earthquakes in India include the:

• Lack of awareness among various stakeholders regarding seismic risk.
• Inadequate incorporation of structural mitigation measures into engineering education syllabi.
• Insufficient monitoring and enforcement of earthquake-resistant building codes and town planning regulations.
• Lack of systems for licensing engineers and masons involved in construction.
• Absence of earthquake-resistant features in non-engineered constructions in suburban and rural areas.
• Limited formal training among professionals in earthquake-resistant construction practices.
• Inadequate preparedness and response capacity among various stakeholder groups

• The National Earthquake Risk Mitigation Project aims to enhance structural and nonstructural earthquake mitigation efforts and reduce vulnerability in high-risk districts prone to earthquakes.
• The project focuses on implementing necessary risk mitigation measures in highly seismic zones.
• The National Disaster Management Authority (NDMA) is responsible for overseeing this project and has prepared a Detailed Project Report (DPR), which is currently under consultation with all stakeholders. Proposed components of the project include establishing a techno-legal regime, strengthening institutions, building capacity, and raising public awareness, among others.

• Ensure the incorporation of earthquake resistant design features for the construction of new structures. Eg Indigenous local techniques for making earthquake-resistant houses (bhunga in Kutch; dhajji diwari buildings in Jammu & Kashmir ; bamboo houses in Assam) should be prepared.
• Facilitate selective strengthening and seismic retrofitting of existing priority and lifeline structures in earthquake-prone areas.
• Improve the compliance regime through appropriate regulation and enforcement.
• Improve the awareness and preparedness of all stakeholders.
• Introduce appropriate capacity development interventions for effective earthquake management (including education, training, R&D, and documentation).
• Strengthen the emergency response capability in earthquake-prone areas

• The National Retrofit Program for India's Earthquake Preparedness was introduced by the Home Ministry in 2014.
• As part of this program, the Reserve Bank of India (RBI) instructed banks to refuse loans for construction projects that do not comply with regulations for earthquake-resistant structures

• India Quake is a mobile application created by the National Center for Seismology to provide real-time information about earthquakes. It aims to disseminate timely updates and alerts regarding seismic events to users.
• Sagar Vani is a smartphone application designed to assist coastal communities by promptly notifying them of ocean-related information and alerts. This includes notifications about high waves and early warnings for tsunamis, aiming to enhance the protection of coastal communities.

• BMTPC is an autonomous organization under the Ministry of Housing and Urban Affairs. It was established to promote modern and cost-effective building materials and technologies. One of its key initiatives is the promotion of life-line structure retrofitting.

• The Sendai Framework for Disaster Risk Reduction, a comprehensive approach to disaster management, includes India among its signatories. India actively engages in the United Nations' International Strategy for Disaster Reduction (UNISDR), indicating its dedication to global disaster risk reduction endeavors.
• The Coalition for Disaster Resilient Infrastructure (CDRI) is an international partnership initiated by the Government of India in collaboration with other nations and international bodies. CDRI aims to bolster the resilience of infrastructure systems against natural disasters and climate change effects.

India is located in a seismically active zone and this necessitates an urgent need for proactive earthquake preparedness and mitigation strategies. The devastation caused by past earthquakes highlights the vulnerability of existing structures and the crucial role played by building codes and town planning regulations. These regulations must be strictly adhered to. Earthquake-resistant construction practices, incorporating indigenous techniques and fostering awareness among stakeholders is very important.

The government's initiatives, such as the National Earthquake Risk Mitigation Project and the National Retrofit Program, are important steps in this regard. Also, the integration of mobile applications like India Quake and Sagar Vani enhances real-time information dissemination and community preparedness. International collaborations, such as the Coalition for Disaster Resilient Infrastructure, position India at the forefront of global efforts in disaster risk reduction. Utilizing technology, strengthening regulatory frameworks, and fostering international cooperation will be pivotal in navigating a resilient path forward against seismic challenges.