【摘要】 检验一个观测变化是否地震前兆异常,需要3个判据:1)有正常背景;2)非干扰影响;3)与地震相关。依据这3个判据,对汶川地震区周围"十五"期间新建立的四分量钻孔应变台站的数据进行分析,结果表明地震之前没有可靠的明显异常变化。进一步对地震前观测应变变化主方向的分析结果表明,它们并非都指向震中。更多还原

【Abstract】 Following three criteria to testify the precursory anomaly before a great earthquake is adopted,1) a normal background;2) not interferences;3) close correlation to the event.According to these criteria,no obvious abnormal changes related to the Wenchuan earthquake were found in preliminary investigation on the recordings of the 4-component borehole strainmeters installed in the Tenth Five Year Project of CEA.A further study on the principal orientations of strain changes before the great shock shows that they did not all point to the epicenter.更多还原