Earthquake

Recently, when an earthquake with a magnitude of 6.6 rocked Nepal, killing a few people and destroying many homes, India experienced strong vibrations.

Why did these tremors occur?

• The India and Eurasia Plate collisions, the primary cause of seismicity in the Himalayas, are cited by the United States Geological Survey (USGS) as the cause of the earthquakes.
• At a relative pace of 40–50 millimetres each year, these plates are convergent.
• This region is one of the most seismically dangerous places on Earth as a result of the northward underthrusting of India beneath Eurasia.
• Some of the deadliest earthquakes have occurred in or near the Himalayas, including those with magnitudes of 8.1 in Bihar in 1934, 7.5 in Kangra in 1905, and 7.6 in Kashmir in 2005.

About Earthquake:

• To put it simply, an earthquake is the ground shaking. It happens naturally. It results from energy release, which creates waves that move in all directions.
• Seismographs are devices that record seismic waves, which are vibrations produced by earthquakes and propagate through the Earth.
• The epicentre is the point on the earth's surface that is directly above the hypocenter, which is where the earthquake begins under the surface.
• Fault Zones, Tectonic Earthquakes, Volcanic Earthquakes, and Human-Induced Earthquakes are the different types of earthquakes.
• The magnitude or severity of the shock determines how the earthquake events are scaled. The Richter scale is the name given to the magnitude scale. The energy released during the earthquake is indicated by the magnitude. The magnitude is given in absolute numbers, ranging from 0 to 10.
• The intensity scale has the name of the Italian seismologist Mercalli. The event's visual damage is taken into account on the intensity scale. The intensity scale runs from 1 to 12.

Distribution of Earthquake:

• Circum-Pacific Seismic Belt: Home to over 81% of the planet's strongest earthquakes, the circum-Pacific seismic belt is the largest earthquake fault zone in the world. It carries the moniker "Ring of Fire."
• The belt is found near the tectonic plate borders, where oceanic crusted plates are subducting beneath other plates. Slip between plates and plate rupture are the primary causes of earthquakes in these subduction zones.
• The Alpine-Himalayan belt, also known as the mid-Continental belt, stretches from Europe to Sumatra and passes through the Himalayas, the Mediterranean, and the Atlantic Ocean.
• About 17% of the greatest earthquakes in the world—including some of the most destructive—occur in this region.
• The third distinct belt is located after the submerged mid-Atlantic Ridge. The ridge indicates the separation of two tectonic plates (a divergent plate boundary).
• The majority of the mid-Atlantic Ridge is submerged and remote from populated areas.

What is India's Seismic Hazard Map?

• Because the Himalayas are technically active young fold mountains, India is one of the most earthquake-prone nations.
• Based on scientific information on seismicity, historical earthquakes, and the tectonic structure of the area, India has been categorised into four seismic zones (II, III, IV, and V).
• The Bureau of Indian Standards (BIS) categorised the nation into four seismic zones by combining the first two zones. Previously, earthquake zones were divided into five zones according to the severity of the quakes.
• Seismic Zone II:
• Area with minor damage earthquakes corresponding to intensities V to VI of MM scale (MM-Modified Mercalli Intensity scale).
• Seismic Zone III:
• Moderate damage corresponding to intensity VII of MM scale.
• Seismic Zone IV:
• Major damage corresponding to intensity VII and higher of MM scale.
• Seismic Zone V:
• Area determined by the seismics of certain major fault systems and is seismically the most active region.
• Earthquake zone V is the most vulnerable to earthquakes, where historically some of the country’s most powerful shocks have occurred.

Read Also: Seismic Mapping of India