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Context

A state of emergency has been declared on Greece’s Santorini and the nearby islands of Ios, Amorgos, and Anafi after a swarm of undersea earthquakes this month, sometimes every few minutes, prompted thousands of people to move to the mainland.

About Earthquake swarm

An earthquake swarm occurs when multiple seismic events of comparable intensity strike a small area in relatively quick succession.

There is no identifiable mainshock. These are short-lived but can continue for days, weeks or even at times months.          

Occurrences throughout the world:

Causes of Earthquake swarm:

Fluid movement.

Slow slip events.

Active volcanism- Stress is accumulated due to movement along the fault line in the earth’s crust.

Tectonic activity.

Hydrothermal activity – underground movement of warm water & gases induce seismic activity.

Induced seismicity – Activities such as Illegal mining, energy extraction due to geothermal energy, wastewater injection.

Characteristics:

No clear mainshock.

Duration – from hours to even months.

Differential magnitude – most of the time low to moderate magnitude but at times larger ones can occur.

Frequent occurrences – small to moderate earthquake in a concentrated area over a short period.

Impacts of swarm:

Redistribution of stress.

Loss of lives & livelihood.

Damage to critical infrastructure.

Sources:

THE HINDU