地震工程学报2017，Vol.39Issue(2)：240-247,8.DOI:10.3969/j.issn.1000-0844.2017.02.0240
大同地震窗P波频散衰减的异常变化特征
Variation Characteristics of the Q Value Deduced from P WaveDispersion Analysis in Datong Window
摘要
Abstract
This paper describes the dispersion characteristics of first-period P waves recorded by seismic stations near Datong window by measuring the medium quality factor (Qm) and analyzing Qm variations before and after the occurrence of earthquakes near and far from Datong window.By applying this method to the SZZ record of the Datong window earthquake sequence from 2001, we obtained the following results: before 3 earthquakes near the Datong window and 6 earthquakes far from the Datong window, the Qm was the high values over 1 times mean square error;but Qm returned gradually the background after these earthquakes.However, after eliminating the influences of epicentral distance and depth, large anomalies were still observed and small anomalies disappeared before the earthquakes.Furthermore, the corresponding rate of earthquake decreased from 0.9 to 0.5.Compared with the frequency of Datong window, the Qm could better reflect earthquake probability.The results of YAY showed that before 1 earthquake near the Datong window and 2 earthquakes far from the Datong window, the Qm were the high values over 1 times mean square error, and false and omitted cases were observed.Minimal changes to the curve were observed after eliminating the influences of epicentral distance and depth.Preliminary analysis suggested that the short-term high-value anomalies of Qm before earthquakes recorded by the SZZ and YAY stations could directly reflect the seismogenic process.However, the Qm recorded by the two stations obviously different before the same earthquakes.Two reasons may explain this phenomenon.The small earthquakes measured by Qm differed between the two stations as these stations were located in different geological and tectonic positions.The SZZ station was located inside the Datong basin, while the YAY station was located in its eastern border.This difference could lead to the different deep medium and broken medium through by seismic wave ray paths and, therefore, marked variations in Qm values.The length and width of Datong window were 60 and 5 km, respectively, so high-value anomalies were limited in this area.From the results of Qm, for the moderate earthquakes which are not only near the Datong window but also far form Datong window, the amplitude of anomaly was almost the same and the distribute range had little change.As such, determining the variation of deep anomalies near or far from Datong window by using the spatial anomaly distribution is difficult.The Datong window showed high-value anomalies before the far-field earthquake of the Shanxi seismic belt because this window is located to the north of the same continental rift.However, the reason why it had high-value anomalies before the earthquakes of Zhangjiakou-Bohai seismic belt which were a few hundred kilometers away, it was possible that the "Y" type of low wave velocity anomaly from Datong volcanoes to below Bohai had played an important role in transmission.关键词
介质品质因子/P波频散衰减/山自皂台/阳原台/大同窗Key words
medium quality factor/P wave dispersion/SZZ station/YAY station/Datong window分类
天文与地球科学引用本文复制引用
王霞,宋美琴,李宏伟,梁向军,李丽..大同地震窗P波频散衰减的异常变化特征[J].地震工程学报,2017,39(2):240-247,8.基金项目
2015年度震情跟踪定向重点工作任务(2015020108) （2015020108）
山西省自然科学基金(2012011029) （2012011029）
中国地震局星火计划(XH15007) （XH15007）
