震前特大地磁异常及其短临预警意义

对地磁记录分析的结果显示,大地震前强烈的地磁异常现象反复出现;在震中附近极震区临震前36h至十几分钟,地磁场的特大异常数值随震级增大而增大。归算到距震中1 km处,Ms=6.0～9.5级破坏性地震的磁场异常值约为102～105 nT,异常强度甚至超过地球磁场量级5.5×104 nT。根据其强度特性及时空分布,这种临震前在震中附近的ULF磁场异常,表现为一种"磁间隙喷发"。由此地磁异常的特性,提出利用大地震前短临地磁异常作为预警信号进行防震预警的探讨,由地磁预警突破目前地震预测预报难的现实困境,有望收到防震减灾的新效果。

强震发生断层的发现及其对所引发次生灾害的防治

强震发生断层特指未来可能发生强震的断层。它源于三次重要地质事件：侏罗纪地壳裂开形成许多断块,各断块以垂直升降为主;新第三纪晚期印度板块向北东推挤俯冲;第四纪晚更新世软流层流动方向改变,致使各断块以水平走滑为主。最终形成强震发生断层的网络。强震发生断层规模宏大。地表上为断续延伸数百公里的条带,宽数米—数百米。深部呈板状,可切穿地壳。强震只发生在强震发生断层上。断层上各处都可能发生6级左右地震,特殊部位会发生7级以上强震。地震时断层内比断层外的烈度陡增23度或更多,断层外侧烈度7°～8°的抗震设防是足够了。强震的发生,乃系上地壳沿剪切面脆性破裂的结果。强震发生断层具有极大的潜在危害。大坝、核电等重要工程及城乡建设均应重视。如果确定有强震发生断层,能避开则避开之,否则应采取相应的抗震措施。建议强震发生断层范围内设置地磁或其他预警系统,以确保安全。

Abnormally large short-term and impending earthquake geomagnetic anomaly implies a possibility of earthquake pre-warning

The study found that strong magnetic anomalies repeatedly took place before big earthquakes. Based on geomagnetic record analysis results,we discussed a possible pattern of the magnetic anomalies prior to earthquake. In meizoseismal area or epicenter,in a time period of 36 h to about 10 min before earthquake,the exceptional big geomagnetic change increases with the magnitude of earthquake. We calculated that,in a place of 1 km from the epicenter,the magnetic anomaly before destructive earthquakes of Ms 6～9 can reach to 102～104 nT(the magnitude of earth magnetic field is 104 nT) ,rather than the magnitude of 10 nT from seismomagnetic effect theories since 1960s. From this we speculated the abnormal magnetic ULF near epicenter before earthquake seems to be an "intermittent magnetic eruption". Accordingly,we proposed that geomagnetic induction earthquake alarm can be a new pre-warning method to surmount hardship in solving the puzzledom of earthquake imminent prediction.