To elucidate the seismic characteristics of earthquakes in the Korean Peninsula, we investigated seismic source parameters of 651 earthquakes that occurred between 2001 and 2014 with magnitudes greater than 1.9. We estimated the seismic moment, corner frequency, and stress drop of an event from S‐wave source spectra. Comparison of our estimates with the results of previous studies confirmed the reliability of our findings. Breakdown in the self‐similarity of an earthquake source may occur at around a seismic moment of 1021 dyn·cm, as suggested by previous studies, although nonnegligible variation still appears in the corner frequency of low‐magnitude events. We also found that earthquakes in two regions, near Pyongyang and on the western margin of the East Sea (Sea of Japan), occurred with low stress drops. These regions have distinctively higher seismicity than other regions. The largest earthquake (Mw 6.2) in the Korean Peninsula in the past century occurred in the low stress‐drop region near Pyongyang. The western margin of the East Sea reportedly has earthquake focal mechanisms that differ from those of earthquakes in other regions in the peninsula. Therefore, we suggest that lateral variation in stress drops in the Korean Peninsula could be related to the distinctive seismic characteristics in these regions.