TECHNOLOGY AND SEVERAL CASES FOR INTER-MEDIATE-AND LONG-TERM PREDICTION OF THE MAGNITUDE 6~7 EARTHQUAKE

In general,the displacement produced by a magnitude 6~7 earthquake is relatively small,even does not reach the surface,so it is difficult to be preserved in geological records.On the other hand,the seismogenic fault of such earthquakes is easy to be considered incorrectly as a non-active fault since Holocene,consequently overlooking the real seismic hazard in the future.To solve this problem,we propose a type of faults that are capable of generating M6~7 earthquakes,but with weak surface activity and cannot produce conspicuous surface displacement.To recognize such faults from geological records,which have no visible evidence of activity since middle-late Pleistocene,is the key to intermediate-and long-term earthquake prediction.The specific procedures of the technology are as follows:First,we determine the seismotectonic setting of the tectonic system in which the target fault lies.Second,we establish the relation between the target fault and other active faults in the same tectonic system,which have records of historical earthquakes or paleoearthquakes.Then we compare varied seismogenic units in the same-order structure,same tectonic system,and varied stages in the same tectonic process.The case studies demonstrate that this is an effective method for intermediate-and long-term earthquake prediction.The cases studied include the Puduhe-Xishan Fault in Kunming City,Hanzhong Basin in the north section of the Longmen Shan Fault zone,Dachuan-Shuangshi Fault in the south section of the Longmen Shan Fault zone,and the Guguan-Guoshun Fault of the LongxianBaoji Fault zone.These faults all show weak activities on the surface and have potential for earthquakes with estimated magnitude 6.5~7.0.In addition,by estimation using this method,the TaoyuanGuichuan Fault of the Longxian-Baoji Fault zone has a seismic risk of M6.0~6.5 earthquake,and the Longxian-Qima-Mazhao Fault is capable of producing an earthquake about M7.5.