In the context of seismic activity of earth, what are swarms? 

Delhi is facing small but frequent shocks and this phenomenon is being compared to Palghar earthquake swarms (Maharashtra).  Option (a) is not correct: The amount of energy released in an earthquake is known as seismic energy. Option (b) is not correct: An abrupt movement of geological materials downhill in response to gravity is known as a landslide. Landslides can be triggered by an earthquake or other natural causes.  Option (c) is correct: According to the Swiss Seismological Service, swarms are numerous earthquakes that occur locally over an extended period, without a clear sequence of highintensity main quakes, preceded and succeeded by lower-intensity foreshocks and aftershocks.