Colombia Earthquake: Causes, Seismic Risk and India’s Vulnerability

Subject: GS 1: Geography

Context: Recently, a 7.4-magnitude earthquake struck western Colombia , killing more than 100 people and becoming the country’s strongest earthquake this century.

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About the Colombia Earthquake

• Aftershocks: The earthquake was followed by two aftershocks measuring 2.8 and 4.8 magnitude, according to Colombia’s Geological Service.
• Vulnerability of Colombia: It lies on the Ring of Fire in the western Pacific region and Andean areas, which are tectonically active regions influenced by interactions among the Nazca, South American and Caribbean plates, with major seismic activity along its western margin.

About Earthquakes

• An earthquake is the shaking of the Earth’s surface caused by the sudden release of energy, generating seismic waves that propagate through the Earth.
• Hypocentre and Epicentre
  • The hypocentre is the point below the Earth’s surface where an earthquake originates and energy is first released.
  • The epicentre is the point on the Earth’s surface located directly above the hypocentre.
• Classification by Depth
  • Shallow Earthquakes: Earthquakes originating at depths of 0–70 km are classified as shallow earthquakes.
  • Intermediate Earthquakes: Earthquakes originating at depths of 70–300 km are classified as intermediate earthquakes.
  • Deep Earthquakes: Earthquakes originating at depths of 300–700 km are classified as deep earthquakes.
• Types of Seismic Waves
• • P-Waves: P-waves are the fastest body waves, arrive first at seismographs, and can travel through solids, liquids and gases.
  • S-Waves: S-waves are slower than P-waves and can travel only through solid materials, making them important for understanding Earth’s internal structure.
  • Surface Waves: Surface waves are generated when body waves interact with surface rocks, travel along the Earth’s surface and are generally more destructive.

Earthquake Vulnerability in India

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The Bureau of Indian Standards (BIS) proposed a revised seismic zonation map under the seventh revision of IS 1893 in late 2025, introducing extreme-risk Zone VI, but the government rolled it back in March 2026 amid economic and developmental concerns.

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