Venezuela hit by Doublet earthquake!

Why in News?

Venezuela has been struck by a rare doublet earthquake, in which a 7.2-magnitude earthquake was followed just 39 seconds later by a 7.5-magnitude earthquake. The disaster has claimed over 235 lives and injured more than 1,500 people, prompting the government to declare a state of emergency.

About Doublet Earthquakes

• A doublet earthquake is a rare seismic phenomenon in which two earthquakes of nearly equal magnitude occur in close succession in the same region.
• Unlike a typical earthquake sequence, where a major quake is followed by smaller aftershocks, both earthquakes in a doublet release comparable amounts of energy.
• Doublets can cause significantly greater destruction because the second major quake strikes before damaged infrastructure and people have recovered from the first.
• According to the US Geological Survey (USGS), Venezuela’s recent earthquakes are an example of this rare phenomenon.
• The earthquakes occurred along the boundary between the Caribbean Plate and the South American Plate, which move past each other at a rate of about 20 mm per year, leading to the accumulation and sudden release of tectonic stress.

About Earthquakes

• An earthquake is the shaking of the Earth’s surface caused by the sudden release of energy accumulated within the Earth’s crust.
• This energy is released along a fault, which is a fracture or break in the Earth’s crust where rocks move relative to each other.
• Continuous movement of tectonic plates causes stress to build up along faults. When this stress exceeds frictional resistance, the rocks suddenly slip, releasing energy in the form of seismic waves.

Focus and Epicentre

• The Focus (Hypocentre) is the point inside the Earth where the earthquake originates and energy is first released.
• The Epicentre is the point on the Earth’s surface located directly above the focus and is usually the first area to experience earthquake waves.
• All natural earthquakes originate within the lithosphere.

Types of Earthquake Waves

Earthquake waves are classified into Body Waves and Surface Waves. 

1. Body Waves: Generated at the focus and travel through the Earth’s interior. They are of two types:

• Primary (P) Waves
  • Fastest seismic waves and the first to reach the surface.
  • Longitudinal (compressional) waves.
  • Travel through solids, liquids, and gases.
• Secondary (S) Waves
  • Reach the surface after P-waves.
  • Transverse (shear) waves.
  • Travel only through solids, making them crucial for understanding the Earth’s internal structure.

2. Surface Waves: 

• Generated when body waves reach the Earth’s surface.
• Travel along the Earth’s surface.
• Move more slowly than body waves but produce the greatest ground shaking and destruction during an earthquake.

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