Q-VALUE IN XINFENGJIANG RESERVOIR REGION ESTIMATED BY Q OF CODA WAVES OF LOCAL EARTHQUAKES

Based on Aki's theory on single backscattering coda wave in applying the coda theory model developed by Herrmann et al. while assuming that the Q is interrelated with the frequency, theoretic curves are calculated in the paper, taking the predominant coda frequency fp(t*, ), the coda slope C(fp, t*, ) and the shape S(p, t*, ) as function of t* for the model 58-1, 63-Band DSL-1 short-period seismographs used in the Xinfengjiang region-data were obtainedfrom 55 local earthquakes, with magnitudes mostly between 3.0 and 5.0. By applying both methods of S-t* and C-t* on the seismic data reco ded with model 58-1 seismographs at four seismic stations in the Xinfengjiang region, the Qo-value of the earth's crust at a frequency around 1.0 HZ in the reservoir region is calculated as between 170 and 300, averaging 23038, and the frequency correlation coefficient being 0.0 to 0.2. Spatial distribution of Q0 indicates that the lowest Q0-value falls on the deep canyon area near the dam. Compared with data obtained in other areas, it is considered that the reservoir region is a relatively stable geologic structure.In addition, the methods of estimating the Q-value of coda waves as well as other issues concerned are also discussed in the paper.