Why in the news?

• As per the study the earthquake swarm that hit Greece is due to magma push in Santorini and  Kolumbo volcanos which share a common magma chamber.

Volcano-Induced Earthquakes

• Definition: A volcano-induced earthquake (volcanic earthquake) is a seismic event generated by magma movement, volcanic gases, or hydrothermal activity beneath or around a volcano, unlike tectonic earthquakes that are caused by plate boundary interactions.
• Causes:
  • Magma Intrusion: Magma forcing its way through cracks and fractures surrounding rocks.
  • Gas & Hydrothermal Pressure: Sudden release of pressurised gases/steam.
  • Volcanic Explosions: Eruptive blasts cause shockwaves in the crust.
  • Structural Collapse: Caldera subsidence or flank collapse generates seismicity.
• Types:
  • Volcano-Tectonic (VT) Earthquakes – Similar to tectonic quakes, caused by rock fracturing due to magma intrusion.
  • Long-Period (LP) Earthquakes – Low-frequency tremors linked to magma/gas movement.
  • Harmonic Tremors – Continuous rhythmic shaking, often a precursor to eruption.
• Characteristics:
  • Usually shallow focus (within 10 km of surface).
  • Often occur in swarms (clusters before eruptions).
  • Lower magnitude than major tectonic quakes, but critical as warning signals.
• Example:
  • Mount St. Helens, USA (1980): Earthquake swarms preceded the eruption.
  • Mount Pinatubo, Philippines (1991): Seismicity indicated magma build-up before catastrophic eruption.
  • Eyjafjallajökull, Iceland (2010): Quakes linked to magma movement prior to eruption that disrupted air traffic.