Relevance: UPSC GS1 (Geography – Geophysical Phenomena); Source: Indian Express, BBC, JMA

A 7.5-magnitude earthquake struck Japan’s east coast, triggering strong ground shaking, building collapses, and widespread tsunami warnings across coastal prefectures. 

What is an Earthquake?

Earthquakes result from the sudden release of energy due to movement along fault lines within the Earth’s crust.
Measurement:

• Magnitude (energy released) → Moment Magnitude Scale/ Richter Scale (Mw)
• Intensity (impact felt) → Modified Mercalli Intensity Scale

What are Tsunamis?

Tsunamis are long-wavelength sea waves generated mainly by undersea earthquakes, volcanic eruptions, or landslides. They travel at high speeds across oceans and rise dramatically on reaching shallow coastal waters.

Ring of Fire

Japan lies on the Pacific Ring of Fire, a highly active tectonic zone encircling the Pacific Ocean known for frequent earthquakes, volcanic activity, and ocean trench formation due to convergent plate boundaries.

Q. Consider the following statements:

1. Tsunamis can be generated only by undersea earthquakes.
   
2. The Moment Magnitude Scale measures the energy released during an earthquake.
   
3. Japan lies at the convergence of multiple tectonic plates within the Ring of Fire.
   

Which of the above statements are correct?
A. 2 and 3 only
B. 1 and 2 only
C. 1 and 3 only
D. 1, 2 and 3