Earthquake swarm

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February 2008 swarm near Mexicali.

Earthquake swarms are events where a local area experiences sequences of many earthquakes striking in a relatively short period of time. The length of time used to define the swarm itself varies, but may be of the order of days, weeks, or months.[1] They are differentiated from earthquakes succeeded by a series of aftershocks by the observation that no single earthquake in the sequence is obviously the main shock.


  • Between February and April 2008 a swarm of 1,000 small magnitude quakes in the United States, referred to as the 2008 Reno earthquakes began in February and ended in November.[2]
  • During the 2011–12 El Hierro eruption. From July 2011 until October 2011, hundreds of small earthquakes were measured. The accumulated energy released by the swarm increased dramatically on 28 September.[3] The swarm was due to the movement of magma beneath the island, and on 9 October indications of a submarine volcanic eruption were detected.[4]
  • Over 500 quakes and aftershocks occurred during a two-week period in February 2008 near Mexicali, along the Cerro Prieto Fault.[5]
  • In 2013, the Santa Cruz Islands experienced a large earthquake swarm with many magnitude 5 and 6 earthquakes occurring in January and February - foreshocks to the 8.0 2013 Solomon Islands earthquake on February 6.
  • In 2014, an area near the California/Oregon/Nevada borders experienced more than 800 small earthquakes over a period of around three months.[6] More than 550 quakes were on magnitude 2.0 or larger.[7]

See also


  1. ^ USGS. "Earthquake Swarms at Yellowstone". United States Geological Survey. Retrieved 2008-08-27. 
  2. ^ Ashley Powers; Thomas H. Maugh II. "Swarm of earthquakes shakes Reno area". Los Angeles Times. Retrieved 2008-08-27. 
  3. ^
  4. ^ Bernardo Marin; R. Mendez (October 11, 2011). "La erupción volcánica submarina de El Hierro libera magma y gases en el océano". El País. Retrieved May 7, 2012. 
  5. ^ Sandra Dibble. "Ground stays still, but residents in quake area rattled". The San Diego Union-Tribune. Retrieved 2008-08-27. 
  6. ^ Associated Press. "As the Earth's crust stretches, swarm of earthquakes tickles remote Nevada desert". FoxNews. Retrieved 2015-10-20. 
  7. ^ Curtis Skinner. "Nevada earthquake swarm increases chance of larger quake". Reuters. Retrieved 2015-10-20. 
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