Variation of seismic source parameters around the southern Korean Peninsula

Abstract:

In this study, we determined seismic source parameters from 557 events with M_L≥1.6 that occurred in the southern part of the Korean Peninsula from 2001 to 2013. A total of 7,267 S-wave trains on three-component seismograms recorded at broadband seismic stations were used for measuring the corner frequency, Brune stress drop and moment magnitude by using the iterative method of Jo and Baag (2001) based on the methods of Snoke (1987) and Andrews (1986). The SNR were calculated for each seismogram to exclude the possible contamination of the records by noise and/or instrumental malfunctioning. For the stable correction of attenuation, we tested several Q factors from the previous studies on those for the Korean Peninsula and found Kim (2007) gave the best result. In this study, as shown by Shi et al. (1998), the stress drop tended to decrease with decreasing seismic moment from the magnitude 3.5. Although there was large scatter in stress drop, however, the stress drops seemed to be constant for the larger events and the average stress drop was estimated to around 45.5 bar. It is interesting that there was a variation in stress drops depending on earthquake location: stress drops of the earthquakes occurred in the East Sea (Japan Sea) and the southwestern part of North Korea were relatively lower than those for the events occurred at other region in the southern Korean Peninsula.