1976年松潘7．2级地震前几种异常波形的记录特征及其在大震短临预报中的意义

本文研究了１９７６年松潘７．２级地震前，几个台站记录到的异常地震波形的形态特征及时空分布特征。异常波形可分为４种形态；震中距小于８０ｋｍ的台站都不同程度地记录到了异常波形；临近地震时，记录中出现的波形数量增多，振幅增大；临震前１０天波形密集，呈现明显的突跳变化。根据异常波形的特征，本文还对异常波形的物理机制进行了初步的研究，认为异常波形的出现是地震前孕震区岩石产生微破裂的结果。

WAVEFOR MANOMALYPRIOR TOTHE SONGPANEAR THQUAKEANDITS VALUETOSHORT-IMMINENTPREDICT1ONOFSTRONGEARTHQUAKES

This paperdealswiththemorphological features of waveform anomalyrecordedat severalstations before the M7.2 Songpan earthquake of 1 976,and the space-time distribution fea-tures.The anomalous waveforms can be divided into four types:the anomalous waveforms wererecorded in verying degrees at all stations(epicenter distance within 80 km );the numbers ofthe waveforms were increased during the approaching of the earthquake;the amplitude was en-larged;the waveforms were densified ten days before the earthquake with obvious skippingchanges. Finally,according to the features of the waveform anomaly,the physical mechanism ofthe anomalous waveforms was studied preliminarily. It shows that the appearance of the wave-form anomaly results from the rock microfracturing in seismogenic area before the earthquake.