A recent development that has caught the attention of the world is a powerful earthquake, measuring 6.1 on the Richter scale, that rattled the border region of Myanmar and India. This shaking of the earth, otherwise known as an earthquake, is a natural phenomenon spurred by the release of energy. This energy discharge results in waves radiating in every direction, creating vibrations we experience as an earthquake.
These vibrations generate seismic waves that journey through the Earth, marking their activity on devices called seismographs. The earthquake originates at a location beneath the Earth’s surface known as the hypocenter. Directly above this point, on the Earth’s surface, is what we call the epicenter.
Understanding Different Types of Earthquakes
There are four major classifications of earthquakes which include Fault Zones, Tectonic Earthquakes, Volcanic Earthquakes, and Human Induced Earthquakes. These categories are based on the cause and geophysical characteristics of the respective seismic event.
Global Distribution of Earthquakes
The most active seismic belt globally is the circum-Pacific seismic belt, also known as the “Ring of Fire”. It is situated along the Pacific Ocean’s rim and is responsible for approximately 81% of the world’s largest earthquakes. This belt is closely associated with tectonic plate boundaries, particularly places where oceanic crust plates subduct beneath another plate. The Alpide earthquake belt, or mid-Continental belt, stretches from Java to Sumatra via the Himalayas, the Mediterranean, and into the Atlantic. This belt is responsible for about 17% of the world’s most significant earthquakes, including some of the most destructive ones. Lastly, another notable belt follows the underwater mid-Atlantic Ridge, where two tectonic plates diverge.
India’s Seismic Hazard Map
India is one of the countries most susceptible to earthquakes due to the presence of the tectonically active young fold mountains – the Himalayas. To better understand and manage these risks, India has been divided into four seismic zones (II, III, IV, and V) based on seismicity, historical earthquake occurrences, and the region’s tectonic setup.
The Bureau of Indian Standards (BIS), the official agency for publishing seismic hazard maps and codes, previously divided earthquake zones into five categories in line with the severity of potential earthquakes. Still, it has since consolidated the previous two zones, resulting in the current four-zone system.
In this division, Zone II corresponds to areas with minor damage from quakes equating to intensities V to VI of the Modified Mercalli Intensity scale (MM). Zone III includes areas that suffer moderate damage, corresponding to intensity VII of the MM scale. Major damage areas, corresponding to an intensity of VII and higher on the MM scale, fall under Zone IV. Lastly, Zone V comprises areas prone to severe seismic activity, including some of the country’s historically most powerful earthquakes, with magnitudes over 7.0 and intensities higher than IX.