Historical earthquake swarm (1565−1566) in the Sangwon Area, Korea

The Korean ancient literature, Joseonwangjosillog, describes the historical earthquake swarm in the Sangwon area from 1565 to 1566 during the seismically active period (1500–1750) in Korea. More than one hundred earthquakes with magnitudes of 3.0– 4.6 occurred collectively in the same place for five consecutive months. Another description in this literature states this phenomenon lasted for eight months to almost one year. There is no evidence related to volcanic or hydrothermal activities around the Pyongyang– Sangwon areas in historical times. One possible explanation for the high seismicity and swarm activity in these areas may be associated with the reactivation of some faults and fault intersections in a highly fractured zone that act as stress concentrators, respectively. No other swarms like this were recognized in the historic records over the past nineteen hundred years.