Earthquake
An earthquake is a phenomenon that occurs without warning and involves violent shaking of the ground and everything over it. It results from the release of accumulated stress of the moving lithospheric or crustal plates.
The earth’s crust is divided into seven major plates, that are about 50 miles thick, which move slowly and continuously over the earth’s interior and several minor plates.
Earthquakes are tectonic in origin; that is the moving plates are responsible for the occurrence of violent shakes.
Figure: Earthquakes
Indian context:
• Around 59% of India's landmass is prone to earthquakes. The three most recent major earthquakes occurred in Gujarat in January 2001, Jammu and Kashmir in October 2005, and Sikkim in 2011.
The Himalayan Mountain range is the youngest fold mountain system globally and remains highly geologically active. Over the last 53 years, this region has experienced four earthquakes with magnitudes exceeding 8 on the Richter scale.
The peninsular region of India consists of a stable continental crust. Although it was previously regarded as having minimal seismic activity, the earthquake in Latur, Maharashtra, on September 30, 1993, with a magnitude of 6.4, led to significant loss of life and severe damage to infrastructure.
The Seismic Zoning Map
India is divided into four Seismic Zones:
• Zone V (Very High Damage Risk Zone): This includes the entire northeastern region, comprising the seven sister states, along with Kutch district, certain areas of Himachal Pradesh and Jammu & Kashmir, as well as the Andaman and Nicobar Islands.
• Zone IV (High Damage Risk Zone): This zone covers parts of the northern region, extending from Jammu & Kashmir to Himachal Pradesh. It also includes Delhi, portions of Haryana, and the Koyna region in Maharashtra.
• Zone III (Moderate Damage Risk Zone): This category encompasses a vast portion of India, stretching from the northern areas, including sections of Rajasthan, down to the southern regions along the Konkan coast, as well as parts of the eastern states.
• Zone II (Low Damage Risk Zone): These zones are adjacent, covering regions in Karnataka, Andhra Pradesh, Odisha, Madhya Pradesh, and Rajasthan, which are classified as low-risk earthquake-prone areas.
Map: Seismic Zones of India
IMPACT OF EARTHQUAKE
| Magnitude (Richter scale) | Intensity (Modified Mercalli scale) | Typical Observations of MM scale |
| 1.0 - 3.0 | I | I. Not felt except by a very few under especially favourable conditions. |
| 3.0 - 3.9 | II - III | Perceptible only to a few individuals at rest, mainly on the upper floors of buildings. Noticeably felt indoors, particularly on higher floors. Many individuals may not immediately identify it as an earthquake. Stationary vehicles might sway slightly, and the vibrations resemble those caused by a passing truck. |
| 4.0 - 4.9 | IV - V | Noticeable indoors by many and by a few people outdoors during the day. Some individuals may wake up at night. Dishes, windows, and doors may rattle, and walls might produce cracking sounds. Feels similar to a heavy truck colliding with a building. Stationary vehicles rock visibly. Experienced by almost everyone, with many waking up. Some windows and dishes may break, while unstable objects can topple over. Pendulum clocks might stop functioning. |
| 5.0 - 5.9 | VI - VII | Specially designed structures sustain minor damage, while ordinary substantial buildings may experience significant damage, including partial collapse. Poorly constructed buildings suffer severe destruction. Chimneys, factory stacks, columns, monuments, and walls may collapse. Heavy furniture is likely to be overturned. Even specially designed structures endure considerable damage, and well-constructed frame buildings may become misaligned. Substantial buildings face severe destruction, including partial collapse, with some structures shifting from their foundations. |
| 6.0 - 6.9 | VIII - IX | Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. Damage considerable in specially designed structures; well- designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. |
| 7.0 and highe | VIII or highe | Some well-constructed wooden buildings are demolished, while most masonry and frame structures collapse along with their foundations. Railway tracks may bend. Very few, if any, masonry structures remain intact. Bridges are destroyed, and railway tracks experience severe bending. Complete devastation occurs. Lines of sight and surface levels are distorted, and objects may be lifted into the air. |
• Property Damage: Earthquakes can severely impact all types of structures, from small cottages to massive skyscrapers, often leading to partial or total destruction. Underground pipelines and railway tracks may suffer damage or breakage. River dams can collapse, causing catastrophic floods. The 1967 Koyna earthquake resulted in significant damage to the dam.
• Loss of Human Lives: Though earthquakes last only a few seconds, they can cause thousands of fatalities. The devastating earthquake in Gujarat on January 26, 2001, led to the deaths of over 25,000 people. The extent of property damage was immense and difficult to assess accurately.
• Alteration of River Courses: Earthquakes can obstruct river channels or alter their natural flow, leading to significant geographical changes.
• Tsunamis: Seismic activity can generate tsunamis, which cause destruction in coastal regions and even submerge
large ships. The 2004 tsunami near Sumatra, Indonesia, resulted in the loss of over 200,000 lives across Southeast Asia, India, and Sri Lanka.
• Mud Fountains: The intense force of an earthquake can push hot water and mud to the surface, creating fountains. The Bihar earthquake of 1934 caused cracks and fissures, covering agricultural fields in knee-deep mud and destroying crops.
• Cracks and Fissures: Tremors can lead to the formation of deep cracks in roads, railway tracks, and fields, rendering them unusable. The well-known San Andreas Fault was created during the San Francisco earthquake in California.
• Landslides and Avalanches: Earthquakes can trigger landslides and avalanches, further increasing destruction and endangering lives.
Challenges and Recommendations in Earthquake Disaster Management
| Challenges | Recommendations |
| Hilly earthquake-prone zones needs retrofitting which is challenging and expensive. Shortage of skilled labour and licenced structural engineers based on competency in designing and constructing earthquake-resistant structures. Poor enforcement of Building codes and safety regulations seen in building collapse in Ahmedabad. Lack of standards on Funding and financing during calamities and inadequate awareness of the National Disaster Relief Fund (NDRF). Problems of Coordination in disaster response system like in case of Bhuj disaster. Lack of effective awareness mechanisms and training of locals for post-disaster operations. | In very high-risk states, a specific department for earthquake management must be established. Hilly areas must be encouraged to adopt the traditional designs like Khasi house design. Granting tax breaks and incentives who construct structures with earthquake resistance. A Single Point of Contact for coordinated response among various departments be established. Skills and capabilities of the local community must be built up. Local bodies be empowered to ensure quick response to disaster as first responders. The funding and technological know-how be ensured in state governments. Research and Development in high-risk regions. For border states, Paradiplomacy in disaster aid can be a useful tool for cooperation. |