华东地区小震P波震源参数特征初探

Study of the P wave hypocenter parameter of the minor earthquakes in East China

摘要选取上海数字化地震台网（台阵）记录到的2001-2004年华东地区发生80次记录较好的小地震。扣除仪器响应、介质响应等，反演单台记录垂直向纵波（P波）震源谱，根据布龙位错模型，计算每个地震单台拐角频率、地震矩、零频谱值、震源破裂半径、应力降等参数，求出每个地震的震源参数的平均值及其均方差，给出了该区小震震源的范围，研究了各参数之间的关系以及各参数与震级（ME）之间的关系。结果表明，华东地区小地震（ME0．8～4．4）拐角频率与震级的关系可以用三次曲线拟合，亦可以将ML2．5～3．0做为分界点用直线分段拟合，后者效果更好；零频谱值的对数与震级关系可以用直线拟合，也可以用二次曲线拟合，效果好于直线拟合；地震矩与震级的关系与零频谱值相似；震源破裂半径的对数与震级的关系可用直线、二次曲线以及三次曲线拟合，3者效果相近；应力降与震级、地震矩以及震源破裂半径之间不存在明显的依赖关系。

In The paper, 80 minor earthquakes well recorded by Shanghai Digital Seismic Network（Array） in East China from 2001 to 2004 were chosen. Eliminating the instrumental response and the medium response and so on, vertical spectrum of P wave recorded at each seismic station was inversed, and parameters of each earthquake such as comer frequency, seismic moment, zero spectrum, rupture radius of seismic source, stress drop and so on were calculated by means of Brune model, then the mean value and mean square error of source parameters each earthquake were obtained. As the same time, the range of minor earthquakes is obtained and the relationship among source parameters, the relationship of ML and each source parameter were analyzed. The result shows that the relationship between magnitude and comer frequency could be fitted by cubic curved, and straight line, respectively, the minor earthquakes of ME 0.8-4.4 and ML 2.5-3.0 in East China, but the later is effective. And not only the relationship between the logarithm of zero spectrum and magnitude can be fitted by straight line but also quadratic curve, but the later is more effective. Beside, rupture radius of seismic source can be fitted by quadratic curve, by cubic curve and by straight line, but three of them have the close effect. Finally, there is no apparent relationship among stress drop and magnitude,seismic moment, rupture radius of seismic source.