Telangana hit by 5.3 magnitude earthquake: Here’s why it is unusual

Telangana hit by 5.3 magnitude earthquake: Here’s why it is unusual

Sub : Geo

Sec : Physical Geo

Context:

• An earthquake with a magnitude of 5.3 struck Telangana’s Mulugu district, causing tremors in Hyderabad and parts of Andhra Pradesh.
• Earthquake Details:
  • Magnitude: The earthquake measured 5.3 on the Richter scale.
  • Affected Areas: Tremors were felt in Mulugu district, Hyderabad, and parts of Andhra Pradesh.
  • Impact: There were no immediate reports of casualties or significant damage, though locals experienced panic.
• Seismic Zones in India:
  • India is divided into four seismic zones:
    • Zone II: Low seismic activity (Telangana falls under this zone).
    • Zone III: Moderate seismic activity.
    • Zone IV: High seismic activity.
    • Zone V: Very high seismic activity.
  • Zone V: Covers about 11% of India, with 18% in Zone IV and 30% in Zone III. The remaining 41% of the country is in Zone II, which includes Telangana.
  • Seismic Vulnerability:
  • Approximately 59% of India is prone to earthquakes of varying intensities.
• Why the Telangana Earthquake Is Unusual:
  • Seismic Classification: Zone II (where Telangana lies) typically experiences low-intensity earthquakes with magnitudes ranging from 3.0 to 5.0.
  • Magnitude of 5.3: The 5.3 magnitude of the Mulugu earthquake is unusually high for Zone II areas.
  • Geological Context: Telangana is part of the Indian Peninsular Shield, which consists of ancient, stable rock formations with little tectonic activity compared to regions near plate boundaries, like the Himalayas.
  • Rare High-Magnitude Earthquakes: While minor tremors may occur due to localized stress or human activities (such as mining), significant natural earthquakes in such stable regions are extremely rare.

Measurement of Earthquake:

Richter Scale (Magnitude):

• Purpose: Measures the magnitude of an earthquake, which indicates the total energy released during the event.
• Scale: The Richter scale is logarithmic, meaning that for each whole number increase on the scale, the earthquake’s magnitude increases by a factor of 10 in amplitude and roughly 32 times more energy is released.
• Range: Earthquakes typically range from 1.0 (micro) to 9.0+ (mega).
  • Minor Earthquakes: Magnitude 3.0 – 3.9
  • Light Earthquakes: Magnitude 4.0 – 4.9
  • Moderate Earthquakes: Magnitude 5.0 – 5.9
  • Strong Earthquakes: Magnitude 6.0 – 6.9
  • Major Earthquakes: Magnitude 7.0 – 7.9
  • Great Earthquakes: Magnitude 8.0+
• Limitations: The Richter scale is less accurate for large earthquakes (magnitude above 7.0) and is less commonly used today for large events.

Moment Magnitude Scale (Mw):

• Purpose: A more accurate and modern way of measuring the magnitude of large earthquakes (especially those above magnitude 7.0).
• Scale: Like the Richter scale, it is logarithmic but considers more factors, including the fault length, fault slip, and rock properties.
  • Provides a more reliable measure of an earthquake’s energy release, especially for large-scale events.
• Range: Similar to the Richter scale, but preferred for measuring very large earthquakes.

Mercalli Intensity Scale (Intensity):

• Purpose: Measures the intensity or effects of an earthquake at specific locations, based on human perception, structural damage, and ground shaking.
• Scale: The Mercalli scale is subjective and varies by location, as the effects of an earthquake can differ greatly depending on distance from the epicenter, local geology, and building structures.
  • The scale ranges from I (not felt) to XII (total destruction).
• Limitations: The Mercalli scale is influenced by subjective reports and human perception, making it less precise than the magnitude scales for comparison across different events.

Body-Wave Magnitude (Mb):

• Purpose: Measures the magnitude of seismic waves that travel through the Earth’s interior (body waves), such as the P-waves (primary waves) and S-waves (secondary waves).
• Application: Typically used for distant earthquakes, where body waves are the first to arrive and can provide early data on the earthquake’s size.

Surface-Wave Magnitude (Ms):

• Purpose: Measures the magnitude based on surface waves, which are the seismic waves that travel along the Earth’s surface.
• Application: Used mainly for larger earthquakes with surface effects, especially those that are felt on the ground.

The Shindo Scale (Japan):

• Purpose: Used primarily in Japan to measure the intensity of an earthquake’s ground shaking, much like the Mercalli scale.
• Scale: Ranges from 1 to 7:
  • 1: Not felt by people, or only a slight shaking.
  • 7: Severe shaking, causing total destruction in affected areas.