Special Issue: Earthquake swarms in Korea

Seismicity over 10 days in 2020 in Haenam, Korea, raised serious concern among residents and authorities, owing to the possibility that this swarm-type activity was a precursor to a large earthquake. Although such seismicity is not common in Korea, swarms had occurred previously in Boryung in 2013 and Baekryung in 2019. It is thus necessary to understand the nature of this swarm-type seismicity. This special issue, entitled “Earthquake Swarms in Korea,” presents the results of detailed investigations by research groups on historical and instrumental observations of swarm-type seismicity in Korea and the implications for estimation of seismic hazard and risk. An earthquake swarm is defined as a sequence of earthquakes occurring in an area within a short period of time. A unique feature of an earthquake swarm is the lack of an identifiable mainshock, in contrast to the commonly observed mainshock-aftershock or foreshock-mainshock-aftershock sequences. Although swarm-type seismicity in Korea has not caused any significant infrastructural or other damage, residents in the affected areas have felt shaking and shown concern. Besides the implications for seismic hazard, swarm-type seismicity provides clues to understanding the mechanism of earthquake nucleation, propagation, and interactions among nearby faults. Case studies in this special issue have taken advantage of state of-the-art instrumentation to identify and characterize swarm type seismicity in Korea. A total of eight papers were accepted for publication in the special issue.