SOURCE PARAMETERS OF EARTHQUAKES IN AND AROUND THE KOREAN PENINSULA DEDUCED FROM SPECTRAL-ANALYSIS

Spectral analysis of > 200 seismograms from seven moderate-magnitude earthquakes in the southwestern Sea of Japan, the Korean Peninsula and the Yellow Sea is performed to determine their source parameters and to discuss their tectonic implications. Short- and long-period records of body and Rayleigh waves are employed. The deduced seismic moments vary from 5.9 x 10(23) to 2.9 x 10(25) dyn cm, and the stress drops vary from 8 to 56 bar. Generally, rather low stress drop values are obtained, which suggests that materials beneath the studied region are highly fractured and softened by the high heat flow related to the opening of the Sea of Japan and the rise of the North China Basin.