摘要
2000年1月15日在云南省姚安县发生了Ms6．5地震，2003年7月21日和10月16日在云南省大姚县发生了Ms6．2、Ms6．1地震。这两个地震序列均发生在滇中块体，震中位置相距42．5km，构造、应力背景相似，但序列类型不同，时间间隔短。为深入研究姚安地震和大姚地震序列的特征，根据昆明区域数字台网记录的数字地震波资料，利用遗传算法计算了2000年姚安地震和2003年大姚地震序列的震源参数。研究结果表明，姚安地震序列和火姚地震序列的地震矩和近震震级有很好的线性关系，它们的地震矩舰均在10^12～10^14N·m，地震矩与震源半径之间呈线性关系。应力降随震级变化不明显。拐角频率和地震矩之间有明显的依赖关系，用最小二乘法拟合拐角频率和地震矩的关系式，利用此关系式可计算出给定地震矩的拐角频率估计值fa，进而可分析实际计算的拐角频率与估计值之差（fc-fa）的时间变化曲线。姚安地震序列和大姚地震序列实际计算的拐角频率与估计值之差（fc-fa）及应力降随时问的变化表现出了不同的特征：姚安地震序列的应力降和拐角频率差值在4．3级和4．6级强余震前均有一个上升-下降过程，反映余震区应力场有一个增高-下降过程；大姚地震序列应力降和拐角频率差值在Ms≥4．6强余震发生之前均会出现高值异常，但在Ms4．6～4．7地震之前出现的高值异常持续时间短，在Ms6．1地震前出现的高值异常持续较长。文中结合两个地震的发震构造，序列类型等特征进行了分析讨论。
On January 15, 2000, an earthquake sequence including the main shock with Ms6.5 occurred in the Yao＇an region of Yunnan Province. On July 21 and October 16, 2003, an earthquake sequence including the main shock with Ms6.2 and Ms6.1 occurred in the Dayao region of Yunnan Province. The epicenters of Yao＇an earthquake and Dayao earthquake are both situated in Dian Zhong block and 42.5 km apart. The tectonics and the stress background of the earthquakes are similar, but the types of two sequences are different and the time interval is short. Based on horizontal-component digital seismograms recorded by Kunming Regional Digital Network, we obtain source parameters of the Yao＇an earthquake sequence in 2000 and the Dayao earthquake sequence in 2003 using genetic algorithms. The results show that there is a good linear relation between seismic moment and local magnitude, the seismic moment is between 1012 and 1014 N · m; the relation between seismic moment and the rupture radius remains a linear correlation. The stress drop seems independent of the local magnitude. The corner frequency increases with the seismic moment decreasing. Based on the expression between corner frequency and seismic mo ment by using least squares fitting, we can obtain the estimated value of corner frequency. Two earthquake sequences show different characteristics. The temporal variation in stress drops and in the difference between the calculated corner frequency and estimated corner frequency of the Yao＇an earthquake sequence is the change from high to low before the strong aftershocks with Ms4.3-4.6, which indicates that there is a process of increasing and decreasing in the stress field of the aftershocks. Whereas the change of stress drops and difference between the calculated corner frequency and estimated corner frequency of the Dayao earthquake sequence has feature of high value before the aftershocks with Ms≥4.7, but the continuing time of high value anomalies before the aftershocks with Ms4.6 and Ms4.7 is shorter than that before the Ms6.1 earthquakes. The seismogenic fault and the type of these sequences were analyzed and discussed.
出处
《地震》
CSCD
北大核心
2006年第1期10-18,共9页
Earthquake
基金
"十五"国家重点科技攻关项目(2004BA601B01-04-03)
"十五"云南省重点科技攻关项目(2001NG46)
关键词
震源参数
姚安地震序列
大姚地震序列
遗传算法
Source parameters
Yao＇an earthquake sequence
Dayao earthquake sequence
Genetic algorithm
