【摘要】 通常4．0级地震，一般只有几天较弱的电磁辐射前兆异常，反映范围一般也仅几十公里。而1995年7月20日涿鹿4．0级地震，其震前电磁异常却非常明显并出现的时间较早，震后信息较强，反映范围也较大，在约16～140km为长轴的近NW向区域内，前兆资料显示了一个由弱变强．再起伏减弱到逐步消失的过程；异常参数重现了方向性、频率升高变化等特征。信息偏强和持续时间较长的原因，可能与震源很浅和一系列的小震活动有关。更多还原

【Abstract】 Generally, an Ms 4. 0 earthquake makes no damage, but on July 20, 1995 a skin depth’s shallow -focus earthquake took place in Xingyuan village in Zhuolu County, and made obvious damages. The Huailai observation station of Hebei earthquake electromagnetic network 16 km from the focus received an obvious electromagnetic radiation abnormal forewarning of the pre --earthquake. The information showed a changing process, which was from weak to strong and from strong to weak and disappeared. And the abnormal characters of direction and frequency changes correlated to the earthquake reappeared.Subjectwords: shallow - focus earthquake ; damage ; electromagnetic radiation ; short term anomaly ;pre-earthquake anomaly.更多还原