Regional moment tensor determination in the southern Korean Peninsula

The Korean Peninsula is a quiet region in terms of seismic activity. Although there are historical records of many large earthquakes that caused severe damage, such major events have not been frequent in recent times, with just a few small- and moderate-sized earthquakes (M ≥ 3) occurring each year. Therefore, the precise analysis of small- to moderate-sized earthquakes is important to understand the characteristics of earthquakes in this region. Broadband seismometers have been deployed in South Korea since 1998 in continually increasing numbers. The current broadband seismic network in Korea is quite dense, and its spatial distribution is nearly homogeneous. This network provides high-quality waveform data and makes moment tensor determination of moderate-sized earthquakes possible. We have inverted regional three-component broadband seismic data for the source parameters of 26 earthquakes ranging in size from Mw 3.2 to 5.0. The moment tensor solutions obtained from time domain waveform inversion show that most of these events have strike-slip faulting mechanisms and that their pseudo P-axis directions are predominantly ENEWSW, with an average azimuth of 72.77°. The source parameters and maximum horizontal shear stress directions obtained in this study can provide basic information that can act as a foundation for detailed seismotectonic studies and seismic hazard analyses.