滇中地区震源机制一致性参数时空分布与强震活动*
付 虹1,王绍晋1,李 丽2,林佳霓3

(1.云南省地震局,昆明 650224; 2.云南大学 环境与资源学院,昆明 650091; 3.中山大学 物理科学与工程技术学院,广东 珠海 519082)

震源机制解; 区域应力场; 震源机制一致性参数

Spatial-temporal Distribution of the Parameters of the Focal Mechanism and Strong Seismicity in Central Yunnan
FU Hong1,WANG Shao-jin1,LI Li2,LIN Jia-ni3

(1.Earthquake Administration of Yunnan Province,Kunming 650224,Yunnan,China)(2.College of Resources and Environment,Yunnan University,Kunming 650091,Yunnan,China)(3.School of Physics and Engineering,Sun Yat-Sen university,Zhuhai 519082,Guangdong,China)

focal mechanism solution; regional stress field; focal parameters consistency

备注

利用云南数字地震台网记录到的地震直达波Pg、Sg振幅资料,采用层状介质中点源位错模型的广义透射系数的快速算法,计算理论地震图的Pg、Sg最大振幅比值,将其与观测值拟合,反演得到1999年至2009年11月14日滇中地区206个中小地震的震源机制解,计算震源机制解应力主轴与相应的区域构造应力场主轴之间的一致性参数,分析震源机制一致性参数时空分布与强震活动的关系。分析表明,强震发生前3年至数月,强震震源区附近出现多个震源释放应力场与区域应力场一致或接近的中小地震,强震就发生在中小震震源机制一致性参数低值分布区内或其边缘附近。

Adopting the amplitude data of the direct Pg and Sg wave recorded by the Yunnan Digital Seismic Network,using the fast algorithm of the generalized transmission coefficient for the Point Source Dislocation Model for the layered media,we calculate the maximum-amplitude ratios of P and S wave of theoretical seismograms,fit the observed values and get the focal mechanism solution of 206 moderate- and small- earthquakes from Jan.1,1999 to the November 14,2009 in central Yunnan through inversion.We calculate the consistency of focal mechanism parameters of the principal stress axis and the regional tectonic stress field,and analyze the relationship between the spatial and temporal distribution of the consistency of focal mechanism parameters and strong seismicity.The analysis showes that several moderate- and small- earthquakes whose stress-release fields are consistent or approximately consistent with the regional stress field occur near the source region of the strong earthquakes,and strong earthquakes will occur in the low-value area and its fringe of the consistent parameters of the moderate- and small- earthquaqkes.