宁夏灵武-吴忠地区地震尾波前兆特性的初步研究

PRELIMINARY STUDY OF THE SEISMIC CODA PRECURSOR CHARACTERISTICS OF LINGWU-WUZHONG REGION IN NINGXIA

摘要:

本文根据K.Aki等的尾波理论,使用台网的三分向地震记录资料,通过数值计算,连续测定了宁夏灵武-吴忠地区三次中强震前后地壳上层介质Q_c值、振幅衰减系数α值以及尾波优势频率随推移时间衰减的指数m值等尾波物理量,并给出了相应的误差估计。结果发现,Q_c值在上述区域中强震前上升,幅度可达常年均值的30%左右,α及m值则在震前下降,或下降后又回升。这表明,经过及时、适当的处理,有可能从区域地震记录的尾波物理量的特征变化中获取强震的前兆信息。

Abstract:

In this paper, on the basis of K.Aki's theory of coda, with the data of three component seismic records from the seismic network, Q_c value for the upper crust medium, α value for the amplitude attenuation coefficient and m value for the attenuation exponent of the coda predominant frequency versus time after origin are continuously estimated, and their errors are also appraised, around three moderate earthquakes of Lingwu-Wuzhong region in Ningxia. As a result, Q_c value increases about 30% of the normal value, α and m value decrease or first decrease and then increase in aforesaid region. before the moderate earthquakes. It shows that it is possible to gain some precursor informations of strong earthquakes from the feature changes of coda physical quantity with the regional seismic record if the available data are properly and timely processed.