紫坪铺水库库区介质衰减、台站响应和震源参数研究

STUDY OF ATTENUATION CHARACTERISTICS,SITE RESPONSE AND SEISMIC SOURCE PARAMETERS OF THE ZIPINGPU RESERVOIR REGION

利用紫坪铺水库数字地震台网和成都区域数字台网中的油榨坪台2004年8月到2008年5月12日汶川大地震前的紫坪铺库区2级以上地震波形资料,采用Atkinson方法计算了紫坪铺水库库区地震波非弹性衰减系数、几何扩散系数和介质品质因子;利用Moya等提出的方法计算了台站场地响应;对震源谱的低频水平和拐角频率进行了联合反演,并计算了紫坪铺库区287次1.6级以上地震的震源波谱参数,同时讨论了它们之间的关系。结果表明:紫坪铺库区Q值与频率的关系为Q(f)=47.8×f^(0.91);场地响应均表现为与频率相关;紫坪铺库区小震地震矩、震级与震源谱拐角频率的依赖关系不明确,这可能与水库诱发地震有关。

Based on digital seismograms recorded by Zipingpu reservoir digital seismic network and YZP station of Chendu Digital Tele-seismic Network from August 2004 to May 2008 before the M8.0 Wen- chuan earthquake,the paper calculates the inelastic attenuation, geometrical spreading and Q of the Zipingpu reservoir region using Atkinson＇s method, and site response using Moya＇s method. Seismic source parameters of 287 earthquakes with M ≥ 1.6 were calculated and the relations between them discussed. Result shows： The relation between inelastic attenuation Q andfis Q（f）= 47.8×f^0.91 ; the site response has correlation with f; and the dependence between seismic moment, corner frequency and earthquake magnitude of small earthquakes is not obvious in the Zipingpu reservoir region,which maybe has something to do with reservoir-induced earthquake.