大同及邻区地震网格化相关分析及预测意义

Correlation analysis of gridding of medium-small earthquakes in Datong and its surrounding areas and implication for earthquake prediction

摘要:

利用华北地区1970～2009年的ML3.0以上地震资料,用相关分析方法,研究了大同及邻区的中小地震空间分布模式及其在该区中强地震前的异常情况。在确定空间范围、时间窗和时间滑动步长后,将地震的空间分布进行网格化再转化为序列;对一个时段内及其稍长时段内的地震空间分布进行序列化,计算两个序列的相关系数并分析相关系数在中强地震前的变化。结果表明,在以1989年大同-阳高5.9级地震震中为中心,取经向和纬向均为1.6°的矩形区域,时段长为3600天,稍长时段取3700天,滑动步长取100天的情况下,1980～2009年的相关系数的时间序列值基本在0.94～1.00之间波动,但在1989年山西大同-阳高5.9级、1991年山西大同5.8级与1999年山西浑源5.6级地震前2年均出现过相关系数小于0.94的异常现象,表明地震的空间分布出现明显变化。分析相关系数异常对于中强地震的前兆意义,得到以下3点认识：①大同及周边地区的中强地震前,可将中小地震空间分布模式发生的显著变化,作为2年尺度的震兆异常,为该区中期地震预测提供时间的参考;②考虑到研究区的限定范围为震中周边0.8°以内,地震时空分布的相关分析结果对于地震地点的预测也是有意义的;③相关分析可以为识别此类地震空间分布模式的异常变化提供帮助。

Abstract:

On the basis of the earthquake（ML≥3.0） catalog in North China from 1970 to 2009,the pattern of temporal and spatial distribution of medium-small earthquake in Datong and its surrounding areas is studied by correlation analysis with the focus on its anomaly before moderate and strong earthquakes.With different spatial scales,temporal scales and time steps,the spatial distribution of earthquakes is converted to a series,then the correlation coefficients between the spatial distribution of medium-small earthquakes in a long-term and a longer time are calculated for the analysis of anomaly before moderate and strong earthquakes.In the study region center on the epicenter of the 1989 Datong-Yanggao earthquake（MS=5.9） within a radius of less than 0.8°,with the time length of 3600 days,the longer time length of 3700 days,and the time step of 100 days,the correlation coefficient from 1980 to 2009 is steady between 0.94 and 1.00,but there was anomaly with the value less than 0.94 in 2 years before the 1989 Datong-Yanggao earthquake（MS=5.9）,the 1991 Datong earthquake（MS=5.8） and 1999 Hunyuan earthquake（MS=5.6）,which indicates the spatial distribution of medium-small earthquake is much different from the steady background seismicity.The implication for earthquake prediction from the anomaly of correlation coefficient is also discussed with the three conclusions：1） Before moderate and strong earthquakes in Datong and its surrounding areas,the obvious change of spatial distribution pattern of medium-small earthquake can be a kind of seismic precursor of 2-year time scale for prediction of earthquake＇s time.2） As the study region is restricted within a radius of less than 0.8°,the result of correlation analysis is also good for prediction of earthquake＇s location.3） The method of correlation analysis in this paper helps recognize the anomaly of spatial distribution of medium-small earthquake.[著者文摘]