Earthquake Swarms

Dear Colleagues,

This Special Issue is dedicated to “Earthquake Swarms”.

Earthquake swarms are puzzling features in seismology. They deviate from the classical definition of the mainshock–aftershock sequence where a major shock ruptures a significant portion of a fault and is followed by smaller events that usually decay in time and taper off in energy following the typical Omori hyperbolic trend. Often, the aftershocks which accompany a mainshock cluster close to the ruptured asperity as a consequence of the stress increase at the borders of asperities that experience high coseismic slip and are affected by an increase in pore–fluid pressure. By contrast, a seismic swarm is typically characterized by mostly small earthquakes with negligible difference in magnitude, which hampers the recognition of a mainshock. Consequently, swarms have different statistical properties and are more difficult to study. The duration of swarms may span a large range of temporal scales, from a few hours to years, and they often recur at the same locations.

Much research has been done in recent years to shed light on the physical mechanisms that lead to the peculiar phenomenon of swarms. The improvement in detection capability of small-magnitude earthquakes is strongly dependent on the implementation of dense arrays of seismic networks, but it also requires sophisticated techniques to isolate all the tiny tremors from continuous seismic data. The location and timing of small earthquakes allow us to obtain a stunningly detailed portrait of the swarm progression along a spidery network of fractures. Swarms are observed in tectonic as well as volcanic environments, geothermal areas, and hydrothermal systems, and they are often associated with fluid migrations and pore-pressure diffusion reducing the strength of faults. However, notwithstanding the large amount of available data, the origin and seismotectonic significance of many swarms is still a matter of debate.

The main aim of this Special Issue is to gather the most relevant research on earthquake swarms worldwide that focuses on all the aspects to investigate these events in detail, encompassing a wide range of seismotectonic settings.

We encourage the submission of manuscripts that deal with innovative methods for detecting and monitoring long-lived swarms, as well as works focusing on the physical basis of swarms The results may help to better unravel the underlying physics of earthquakes. 

Both review and original papers are welcome.

Potential topics of the Special Issue include but are not limited to:

• Earthquake swarms;
• Earthquake mechanics;
• New developments in detection and data processing of small earthquakes;
• Structural geology and tectonics;
• Induced seismicity;
• Geothermal reservoir;
• Statistical seismology.

Dr. Maria Grazia Ciaccio
Dr. Paola Baccheschi
Dr. Diana Latorre
Guest Editors

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• High-resolution earthquake detection
• Natural and induced seismic swarms
• Fluid flow and stress-triggering
• Earthquake source mechanism
• Statistical analysis
• Volcanic swarms