Seismic Scatter Associated with Earthquakes that Ended a Quiescent Period in Southeastern Korea

Abstract

Two recent hazardous earthquakes ( M 5.8 and 5.5) in southeastern Korea were the largest instrumentally recorded inland events after an abnormally long, seismically quiet, period. In this study, we used coda envelope tomography to observe the heterogeneities related to active faults, which can, in turn, help mitigate seismic hazard in the area. However, this tomography was not able to detect faults in the intraplate region. By separating the periods before and after the M 5.8 earthquake, we analyzed 225 and 204 seismograms obtained from 127 and 86 events, respectively. Both periods showed time-varying heterogeneity correlated with fault activity. Adding 446 seismograms from 235 aftershocks of the two events to the analysis showed us a heterogenous structure that closely correlated to the active faults where the recent earthquakes originated.