The Research Of Longmen-shan Fault Seismic Activity

Longmen-Shan fault zone is form the QingChuan to Luding and viaBeichuan, Mao, Mianzhu, Wenchuan, Dujiangyan, Dayi, Baoxing County whichconsistent with the Longmen-Shan direction that distribute from Northeastto southwest and the longmen-Shan fault zone is mainly composed of threethrust faults which have NE-SW direction and from West to East are Wenchuanto Maoxian fault (Posterior segment of the Longmen-Shan fault zone), theYingxiu to Beichuan fault (the central fault zone) and Guanxian to Anxianfault (Anterior segement of the Longmen-Shan fault zone) respectively.The fault zone have been occurred5times Ms6.0to Ms6.5earthquakes andthe largest one occurred in this fault zone is the Wenchuan Ms8.0earthquake in2008.Wenchuan earthquake made the fault surface of Yingxiuto Beichuan and Guanxian to Anxian region ruptured at the same time andthis phenomenon caused the strong focus by the international academia.Therefore the mainly content of this paper is calculation the seismicityparameters of Longmen-Shan earthquake fault zone,then compare thegeological surface feature of the Longmen-Shan fault zone and the DeepVelocity Structure of this fault zone which hope to find the connectionamong those data.The seismicity parameters spatial scanning of the Longmen-Shan faultzone revealed that the Longmen-Shan Fault Zone from Wenchuan to Maoxian,Beichuan to Pingwu has anomalies low b-value and the a-value has the samesituation among those region which indicating that the region’s seismicactivity frequency is low, and the expected magnitude a/b-value is high.so it can be concluded that before the Wenchuan earthquake, the two regions was under the heavy stress blocking state space scanning diagram alsoshows that in the other region of the Longmen-Shan fault zone, Hongya hasa relatively low b value, low a value which this area have no obvious damagein the Wenchuan earthquake, so, this fault zone may be in the process ofstress accumulation, it is likely to occur strong earthquake in the futureGeological characteristics of surface of the Longmen-Shan fault zoneshows that Wenchuan earthquake made the two mainly fault of theLongmen-Shan fault zone which are the central fault zone (Yingxiu toBeichuan) and the mountain front fault segment (Guanxian to Jiangyou)produced a huge surface rupture. Those two regions’ spatial scanningshows that these two area has a very low b-value, a-value and the higherexpected magnitude before the Wenchuan earthquake. So this may explainthe reason that these two fault have such a huge damage scale.In addition, deep velocity structure of Longmen-Shan fault zone showsboth sideways of the former mountain fault zone and the main central faultzone, the seismic wave appeared a apparently anomalous velocity in thedifferent depth (fault zone in southern has low velocity), this showsthat the Longmen-Shan fault zone seismic wave velocity have a boundariesOn the other hand,compared the anomalous area of the deep velocitystructure of Longmen-Shan fault zone and the seismicity parametersspatial scanning, we can infer that at the shallow area there is a goodcorrelation between these two data,but with the depth increase,theconnection between them has been more and more weak. So we conclude thatrelationship of those two data may not have universality...