Spatial Distribution of Coda Q in South Korea

Abstract

Analyzing spectral attenuation of coda waves, we first mapped coda Q- values in the crust over the whole of South Korea. During the period from 1995 to 2004, we selected 574 north？south-component seismograms with epicentral distances less than 100 km from 328 earthquakes with magnitudes between 1.4 and 5.2. We estimated coda Q-values using the single isotropic scattering model at center frequencies of 1.5, 3, 6, 9, 12, 15, and 18 Hz, and found significant spatial variation over all frequency ranges and strong frequency dependence of coda Q in the region. The estimated coda Q-value at 1 Hz (Q0) and the n-value ranges are 80？300 and 0.4？1.1, respectively. The values have strong correlation with the regional geology in the Korean peninsula. Low Q0-values are mainly obtained in the regions comprising sedimentary strata in southeastern South Korea, whereas granite regions in the northern part of South Korea show high Q0. The Q0-values in the study area agree well with those of the eastern China and Kyushu, western Japan. Furthermore, our n-values are also in good agreement with those of Japan.