Aftershocks Earthquakes that follow a large earthquake (the mainshock) in an earthquake sequence.
Earthquakes typically occur in sequences that may include foreshocks, the mainshock (the largest event or events), and aftershocks. Earthquake sequences without a clear mainshock are called swarms.
Aftershocks generally refer to the smaller earthquakes that follow a mainshock within certain spatial and temporal windows. However, the criteria for choosing these windows are somewhat arbitrary. Typically, aftershocks are defined within an area around the mainshock’s source region (i.e., the ruptured fault segment, which is about 50–100 km long for a magnitude 7.0 earthquake). Most aftershocks occur on the main rupture surface; hence, they are often used to define the complex geometry of the rupture plane. However, in many cases, especially for earthquakes in subduction zones, the aftershock area increases significantly following the mainshock (Tajima and Kanamori 1985)...
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