Why in the news?
A powerful 7.7-magnitude earthquake struck Myanmar on March 28, causing buildings to collapse in Mandalay and bringing down a skyscraper under construction in Bangkok. Here, we have discussed about Earthquake disaster and its causes, impact and preparedness.
What is an earthquake?
An earthquake is a sudden shaking or trembling of the Earth’s surface caused by the movement of tectonic plates or volcanic activity, thereby releasing energy. Also, India is located in a seismically active region, and the country is prone to earthquakes, with over 59 percent of India’s land area under threat of moderate to severe seismic hazards.
Causes of Earthquake Disaster in India
1. Tectonic activity
- Faulting: Sliding and moving past each other of rocks along the faults causes an earthquake, as it stores energy in the form of seismic waves.
- Plate Boundaries: Most of the earthquakes take place along plate boundaries where tectonic plates collide, separate, or slide past each other.
- Convergent Boundaries: Where plates collide, one plate may slide beneath the other (subduction), as a result, causing earthquakes and potentially volcanic activity.
- Divergent Boundaries: Where plates move apart, magma rises to the surface, therefore causing earthquakes and volcanic eruptions.
- Transform Boundaries: Where plates slide past each other horizontally, friction and stress build up, eventually releasing as earthquakes.
2. Volcanic Activity:
- Volcanic Earthquakes: Where active volcanoes are present, and movement of magma of these volcanoes takes place within the Earth’s crust.
- Stress Changes: It occurs due to a change in stress in the surrounding rocks from which magma passes frequently.
- Land Subsidence and Cracks: Volcanic earthquakes can cause the ground to sink or crack, and can also be associated with volcanic eruptions.
3. Anthropogenic (Human-Induced) Causes:
- Reservoir Formation: Large dam and reservoir construction are also major factors for altering the stress in the Earth’s crust, eventually triggering earthquakes.
- Resource Extraction: Extraction of resources like minerals, groundwater, ores, etc., causes changes in the stress in Earth’s crust, which results in earthquakes.
- Hydraulic Fracturing (Fracking): The injection of fluids deep into the Earth’s crust during hydraulic fracturing can trigger earthquakes.
Earthquake Zones in India
The Bureau of Indian Standards (BIS) has divided India into four seismic zones based on the level of seismic hazard.
ZONE V- 11% , ZONE IV- 18%, ZONE III- 30%, ZONE II- 41%
Impacts of Earthquake Disaster
(a) Structural damage
Earthquakes can destroy buildings and other critical structures. In India, above 90% casualties have occurred due to the collapse of houses and other structures.
(b) Surface Rupture & Ground Displacement:
The primary earthquake hazard is surface rupture. It can result from vertical or horizontal displacement on either side of a ruptured fault. If ground displacement occurs in a broad area, it can cause significant damage to roads, trains, and pipelines.
(c) Tsunamis:
Earthquakes that occur beneath the water have the potential to cause tsunamis. The most likely scenario for a massive tsunami is a large (M7 or greater) subduction-related earthquake.
(d) Liquefaction:
Weak strength of loosely packed,water-logged sediments causes liquification of soil due to intense ground shaking. Since soil temporarily behaves like a viscous liquid, it can be lethal if under a house or critical infrastructure during earthquakes.
(e) Fires:
Fires are often linked to earthquakes because fuel pipes rupture and electrical wires are destroyed when the ground shakes. Also, Earthquakes can cause economic disruption, as businesses and industries are forced to close, and people are unable to work.
India’s Preparedness for Earthquake Disaster
National Centre for Seismology:
It works under the Ministry of Earth Sciences, monitors earthquakes through 115 observatories. Furthermore disseminates information to state and central disaster authorities for timely mitigation measures.
National Earthquake Risk Mitigation Project:
It involves the adoption, enforcement, and updation of a Techno-legal Regime, institutional strengthening, and public awareness. It is approved in seismic zones 4 and 5.
Seismic micro-zonation of cities:
National Centre for Seismology does demarcation(seismic micro-zonation) of cities with a population of more than 5 lakh. As its purpose is to ensure earthquake resilient infrastructure as well as safe urban planning, to minimise damage and loss of life.
Awareness campaign by NDMA:
The National Disaster Management Authority (NDMA) of India conduct regular awareness campaigns every year. It leverages print, electronic and social media from time to time to sensitise programs on prevention and preparedness.
Earthquake Disaster Risk Index.
The index of cities in Seismic Zones IV and V is an attempt to estimate the earthquake risk of the country to help reduce the social and economic consequences of an earthquake.
Way forward
- Building Codes and Standards: India has established building codes and standards for earthquake-resistant construction. It is important to strictly enforce these codes and standards to ensure that new buildings withstand earthquakes.
- Retrofitting and Reinforcement: Older buildings (not meeting current earthquake-resistant standards) can be retrofitted or reinforced to improve their seismic performance.
- Emergency Response Planning: Planning for emergency response is critical for minimising the impact of earthquakes. This includes developing evacuation plans, establishing emergency shelters, and training personnel on how to respond to earthquakes.
- Research and Monitoring: Research and monitoring can help improve understanding of earthquakes and their causes, and methods for predicting and mitigating their impact.
- Land-Use Planning: Limit development in areas that are prone to earthquakes. Also, ensure that if new development is taking place, then it should be in a way that minimises the risk of damage.
Conclusion
With collaborative actions and a coordinated approach of all stakeholders, effects as well as causes of the earthquake can be managed, and a safer rural and urban region with earthquake-resilient infrastructure can be made.