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全新世以来岷江断裂带古地震参数是地震潜势评价的重要基础.通过对比漳腊盆地黑斯沟沟口T2阶地前缘的大型探槽剖面的沉积层,将沉积序列分为两套地层.下部为青灰色河流相冲洪积砾岩层,上部为浅黄色至灰白色滨湖相粉细砂层、冲洪积相砾石层夹泥炭层.通过对比地层的错动、坎前堆积、地层产状变化等要素识别出3次古地震事件,同震垂直落差约1.5m.依据地震震级、同震位移、同震破裂尺度之间的关系,可推测岷江断裂带古地震震级约7.1.初步判定复发周期在2 557~3 410a.考虑目前断层陡坎的埋藏形态接近震前形态,离逝时间亦较长,汶川地震后,该区地震危险性应引起重视.
The Paleoearthquake parameters of the Minjiangjiang fault zone have been the basis of the seismic potential evaluation since the Holocene.The sedimentary sequence is divided into two sets of strata by comparing the sedimentary layers of the large trench at the T2 terrace front of the Hadesgou Mizoguchi in Zhangla Basin. The lower part is the bluish-gray river flood alluvial conglomerate layer, the upper part is light yellow to gray-white lake facies fine sand layer, the alluvial-graded gravel layer is sand peat layer. By comparing the stratigraphic dislocation, Changes and other elements identified three paleoseismic events, the coseismic vertical drop about 1.5m.According to the magnitude of the earthquake, coseismic displacement, coseismic rupture scale, it can be speculated that the ancient earthquake magnitude of the Minjiang fault zone is about 7.1. Preliminary determination of recurrence Period is from 2 557 to 3 410a. Considering that the burial pattern of the current fault scarp is close to the pre-earthquake morphology and the time of exiting is longer, the seismic hazard in this area should pay attention to after the Wenchuan earthquake.