Earthquake swarm

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Recently, a seismic swarm has hit the Reykjanes peninsula in southwest Iceland with more than 5,500 small earthquakes in the last three days.

About earthquake swarm

  • It is a series of many (sometimes thousands) low-intensity earthquakes without a discernible main shock that can occur over weeks in active geothermal areas.
  • When seismic energy piles up inside the Earth and is released in small amounts from certain points, such a series of earthquakes can occur.

What causes swarm sequences?

  • Fluid movement:
    • In volcanic environments, this can be fluid released from deeper magma or circulating within active geothermal areas (in volcanic areas such as the Taupō Volcanic Zone).
    • The earthquakes triggered by fluids occur as fault slip on the cracks and faults through which the water is moving.
  • Active volcanism:
    • Magma movement can also act as the ‘driving mechanism’ for swarms, creating the earthquakes as magma-filled cracks push their way through the Earth’s crust.
    • In such a case the earthquakes commonly occur near the crack tip (ahead of the magma where the crack is starting to open), or off to the side of the crack.
  • Slow-slip events
    • A slow-slip event is essentially an earthquake in slow-motion, and typically involves centimetres to tens of centimetres of movement along a fault, over weeks to years.
    • We commonly see slow slip events at the Hikurangi subduction zone, usually at least one or two per year. 

Key facts about Reykjanes peninsula

  • It is a peninsula in South West Iceland, characterized by immense lava fields, volcanoes, and heightened geothermal activity.
  • It runs along the Mid-Atlantic Rift, where the Eurasian and the North American tectonic plates are drifting apart. 

Q1) What is Mid-Atlantic Ridge?

It is a major underwater mountain range that runs down the center of the Atlantic Ocean. It is a divergent tectonic plate boundary where the North American Plate and the Eurasian Plate are moving away from each other. This geological feature extends for thousands of kilometers from the Arctic Ocean in the north to the Atlantic Ocean in the south, essentially dividing the Atlantic Ocean into two halves.

Source: Iceland hit by ‘seismic swarm‘ of small earthquakes in volcano warning