DETERMINATION OF Q-VALUE BY THE CODA WAVE FOR A PORTION OF THE SICHUAN PROVINCE

By using the theory of coda waves developed by K. Aki for an earthquake recorded at a number of stations and the equations based on the assumption that each earthquake has a definite seismic moment, the Q-value of the crustal medium at shallow depth of a portion of the province of Sichuan has been determined, taking the results published by Chen Yuntai et al.8 as a basis.The results thus obtained reveal a definite character of variation with direction of the attenuation of coda waves. Besides, earthquakes occurred from 1971 to 1975 give three sub-regions of the province, each of different Q-value. It is also noted that in the region, of low Q-value occurred an earthquake of magnitude 7.1.