【摘要】 2013年4月20日芦山M_S7.0地震前,四川省姑咱台四分量YRY-4型钻孔应变仪记录到显著的高频应变畸变信号。为了避免该畸变信号的高频部分在时频演化过程中发生频率混叠现象,同时便于讨论同一研究频段内震前更早记录到的弱应变异常时段与显著应变异常时段的相关性,本文对2012年1月1日至2013年4月20日期间姑咱台的钻孔应变数据进行了时频分析,并使用时域分段的小波变换方法,在局部时频谱中提取了应变异常,分析了各应变异常的频率相关性。结果表明,研究频段内存在两个峰值频率,峰值频率附近频段内弱应变异常时段与显著应变异常时段的相关系数为0.85,统计出的无震时段与其显著应变异常时段之间的相关系数只有-0.007,且已排除远震以及外界环境带来的干扰,因此该峰值频率作为异常频率的可信度较高,由此推测四分量钻孔应变仪所记录到的两种不同程度的应变畸变信号的演化过程可能与芦山M_S7.0地震相关。更多还原

【Abstract】 Before the 20 April 2013 Lushan M_S7.0 earthquake,a significant high frequency strain distortion signal has been recorded by the four-component YRY-4 borehole strainmeter at Guzan station in Sichuan Province. In order to avoid the frequency aliasing phenomenon of the high frequency part of the distortion signal in time-frequency evolution process in the same spectrum,and for the purpose of discussing the correlation between the weak strain anomaly period recorded earlier and the significant strain anomaly period in the same studied frequency band before the earthquake,this paper carried out time-frequency analysis on the borehole strain data of Guzan station during the period from 1 January 2012 to 20 April 2013 by using the continuous wavelet transform method. The results show that there are two peak frequencies in the studied frequency band,the correlation coefficient between the weak strain period and significant strain anomalous period near the peak frequency reach 0.85,and the correlation coefficient between aseismic period and significant strain anomalous period is only-0.007. Therefore,the peak frequencies is highly reliable as the anomalous frequency,and the evolution of two kinds of deformed strain signals recorded by four-component borehole strain gauge may be related to Lushan M_S7.0 earthquake.更多还原