The earth beneath us is in constant motion, shifting and adjusting to pressures unseen by the human eye. A recent series of tremors in India, triggered by a 6.6 magnitude earthquake in Nepal, has raised concerns and awareness about this natural phenomenon. Many are wondering about the causes and impacts of these seismic activities.
Understanding the Cause of Earthquake
The United States Geological Survey (USGS) attributes the recent tremors in India to the collision between the Indian and Eurasian tectonic plates. Tectonic plates are pieces of the Earth’s crust that fit together like a jigsaw puzzle. When these plates converge or move towards each other, it can lead to significant geological events, such as earthquakes.
The Indian and Eurasian plates are converging at a relative rate of 40-50 millimeters per year. This convergence leads to the under thrusting of the Indian plate beneath the Eurasian plate, generating numerous earthquakes. This has made the Himalayan region one of the most seismically active zones on Earth.
The Science Behind Earthquakes
An earthquake is the result of a sudden release of energy in the Earth’s crust that creates seismic waves. These waves travel in all directions, causing the ground to shake and vibrate.
The vibrations, known as seismic waves, are recorded on instruments called seismographs. The origin or starting point of an earthquake beneath the Earth’s surface is known as the hypocenter, while the location directly above it on the Earth’s surface is called the epicenter.
Several types of earthquakes exist, including those caused by fault zones, tectonic activities, volcanic activities, and even human-induced activities. The severity of an earthquake is often measured using the Richter or Mercalli scales, which measure the magnitude and intensity of the shock, respectively.
Global Distribution of Earthquakes
Earthquakes occur predominantly in certain regions, like the Circum-Pacific Seismic Belt, also known as the “Ring of Fire”. This region, along the rim of the Pacific Ocean, accounts for about 81% of the planet’s largest earthquakes.
Other significant seismic zones include the Alpine-Himalayan Belt or Mid-Continental Belt that stretches from Europe to Sumatra through the Himalayas and the Atlantic, and the underwater Mid-Atlantic Ridge where two tectonic plates are spreading apart.
India’s Seismic Hazard Map
India, due to its geographical position and geological structure, is particularly vulnerable to earthquakes. Its young fold mountains, the Himalayas, are tectonically active, increasing the risk of seismic activity.
The country is divided into four seismic zones — II, III, IV and V — based on their seismicity, historical earthquake events, and tectonic setup. Seismic Zone V, comprising major fault systems, is the most active and susceptible to powerful earthquakes.
While earthquakes are natural and unpredictable phenomena, understanding their causes and distribution can aid in developing effective mitigation strategies and response measures.