In News:

Scientists from the University of Oxford have proposed a new method to monitor volcanic eruptions by using the seismic phenomenon of shear-wave splitting, demonstrated at Mount Ontake in Japan.

What is Shear-Wave Splitting?

• Shear-wave splitting is a seismic phenomenon where shear (S) waves split into two components that travel at different speeds based on their polarisation.
• Occurs when waves pass through aligned cracks or fractures in subsurface rocks.
• Movement of magma and volcanic fluids changes stress conditions, causing rock cracks to open or close.
• These changes influence the speed and direction of shear waves.
• Increased shear-wave splitting can indicate rising internal pressure, serving as a potential early warning for volcanic eruptions.

Mount Ontake – Key Facts

• Type: Active stratovolcano
• Location: Honsh? Island, Central Japan, near Tokyo
• Status: Japan’s second-highest volcano
• Part of the Pacific Ring of Fire
• Major Eruption:
  • Year: 2014
  • Type: Phreatic eruption (steam-driven)
  • Casualties: 60+ people, mainly hikers
  • Notably occurred without significant seismic warning
• Phreatic Eruptions:
  • Caused by steam pressure from heated underground water
  • Do not involve new magma
  • Difficult to predict using conventional methods