Category:Earthquake clusters, swarms, and sequences

For identifying a broad class of articles about multiple earthquake events, such as clusters, sequences, swarms, and doublet earthquakes, and also for historical earthquakes where there is insufficient data to distinguish a main shock from a nearly as strong fore- or after-shocks. Does not include lists of foreshocks and aftershocks associated with a main shock.

In general: A cluster is any group of earthquakes of similar type and magnitude in a given area over a period of months, but not including aftershocks (resulting from marginal adjustments to a main shock, and steadily diminishing in size and frequency), while a swarm is an elevated level of low and moderate magnitude events in a period of months that lack a significant main shock, often attributed to localized crustal stress resulting from the filling or emptyng of reservoirs, or extraction or injection of fluids. Sequences are distinct events recurring at intervals of decades or centuries in a given region, and believed to result from a continuing tectonic process. Doublet earthquakes are two (or more) related earthquakes of similar size and focal mechanism that occur closely in time and location; they have been attributed to interuptions in the rupture process that causes part of the earthquake to be delayed.