京津地区Q值及平均应力降的分布特征

本文用P波初动半振幅和半周期直接测定介质的品质因素（Q值）和小震震源参数的方法,测定了京津地区十个区两个时间段介质的平均品质因数及小震震源参数。结果表明:唐山大震前在平谷台到唐山震区的路径上平均Q值明显的高,大约是其它区的一至二倍,并且唐山震区平均应力降最大,比其它区约大一个数量级,这说明唐山大震前这个地区介质的强度较高,整体性较强,并比其它地区积累了较高的应力。在这个基础上,对京津地区的地震趋势提出了看法。 此外,本文还给出了京津地区中小地震震源参数间的经验关系。

DISTRIBUTION CHARACTERISTICS OF THE QUALITY FACTOR Q AND THE AVERAGE STRESS DROP IN THE BEIJING-TIANJIN DISTRICT

In this paper, the average quality factor Q of the medium and the source parameters of some small earthquakes for ten regions in the Peking-Tianjin area during two time intervals were determined by using the half-period and half amplitude of the initial motion of P wave. The results show that before the great Tangshan earthquake, the average quality factor Q along the path from Pinggu seismic station to the Tangshan region is about one to two times larger than that of the neighbouring regions. The average stress drop of the medium and small earthquakes in the Tangshan region is about one order of magnitude greater than that in neighbouring region. It means that before the great Tangshan Earthquake, the strength and integrity of the medium of this region is rather high. The accumulated stress is higher than that in neighbouring regions. On this basis, some idea concerning the tendency of future seismic activity is presented.In addition, an empirical relationship among the source parameters of medium and small earthquakes in the Beijing-Tianjin area is given.