We examined 2-D heterogeneous structure in the eastern Hokkaido region, using the S-wave coda amplification factor (CAF) with seismic storong-motion date of Kyoshin Net(K-NET). CAF is defined as the spectral ratio of coda waves among different stations after corrections for source, site, and overall propagation.(i.e,cada-Q) effects. Confirming that code-Q values are nearly independent of both source and station, the site effect at each station was esetimated by the coda-normalization method. The source effect was removed by taking the spectral ratio of S-wave coda among stations for each earthquake. We evaluated the CAF value of each source-station pair for three components,using 95 seismograms for five local earthquakes recorded at 21 stations of K-NET. A map of CAF values at the frequency band of 16 Hz shows a systematic variation, implying that heterogeneities are concentrated at the central area (Shibeccha) in the eastern Hokkaido region, manifested locally as a large degree of scattering
