SEPARATION OF SCATTERING ATTENUATION AND INTRINSIC ABSORPTION IN JAPAN USING THE MULTIPLE LAPSE TIME WINDOW ANALYSIS OF FULL SEISMOGRAM ENVELOPE

Two seismic wave attenuation factors, scattering attenuation (Q(s)-1) and intrinsic absorption (Q(i)-1), can be determined from estimates of two parameters, the reciprocal of extinction length L(e)-1=(Q(s)-1+Q(i)-1).omega/v and seismic albedo B0=Q(s)-1/(Q(s)-1+Q(i)-1), where omega and v are angular frequency and seismic wave velocity, respectively. These parameters are measured using the multiple lapse time window analysis method over frequency bands of 1-2, 2-4, and 4-8 Hz from 16 stations located throughout Japan. In the analysis, time-integrated seismic wave energy from earthquakes having hypocentral distances less than 120 km and focal depths less than 40 km are compared with simulations of multiple isotropic scattering based on the assumption of spatial uniformity of Q(s)-1 and Q(i)-1. The modified coda normalization method is used to correct for sources and site effects, where the spatially non uniform distribution of the coda wave energy is considered. The L(e)-1 estimates do not have a distinct frequency dependence. but the B0 estimates do: 0.2-0.7 for 1-2 Hz and 0.1-0.3 for 4-8 Hz. The results mean that Q(s)-1 is similar to Q(i)-1 for 1-2 Hz but is 3-5 times smaller for 4-8 Hz and that the frequency dependence of Q(s)-1 is larger than Q(i)-1. Analyses using different components of motion and different window lengths give nearly the same results. Coda attenuation (Q(c)-1) estimates based on the single scattering approximation are nearly equal to intrinsic absorption Q(i)-1 rather than to total attenuation (Q(s)-1+Q(i)-1) for Japan.