龙门山断裂带南段错断晚更新世以来地层的证据

THE EVIDENCE OF THE SOUTH LONGMENSHAN FAULT ZONES CUTTING LATE QUATERNARY STRATUM

在野外实地考察基础上,研究人工开挖剖面并使用现代测年技术后,发现龙门山断裂带南段的前山断裂和中央断裂自晚更新世以来发生过强烈的活动。可以分辩出龙门山前山断裂南段大川- 双石断裂错断距今5-74 万a 以来的冲积层,垂直位移1-74m ;中央断裂南段五龙断裂在错断距今9 万a 左右的冲洪积地层后,被距今约7-85 万a 的坡积层覆盖,剖面上地层的垂直位移为0-73m 。

The Longmenshan fault zone is a boundary fault between the Tibet Plateau and western Sichuan foreland basin which controls the seismicity of the Longmenshan region. Two geological profiles had been dug in the south segment of Longmenshan fault zones. It is found that the reverse Wulong fault (south segment of the Longmenshan center fault zone), at the northern of Wulong village, offsets the stratum of TL age 92.0±7.2 thousand years, and is covered with the layer which TL age is 78.5±6.1 thousand years, the vertical displacement is 0.73m. The reverse Dachuan shuangshi fault (south segment of the Longmenshan front fault zone), at the northern of Daxi village, offsets the stratum which TL age is 57.4±4.5 thousand years, the height of the fault scarps is about 1.74m.