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摘要:
在挠曲悬臂梁模型的基础上，利用二维正、反演相结合的方法，对琼东南盆地近垂直于盆地走向、过陆架、陆坡的测线1岩石圈不同圈层的伸展因子进行计算。其中，上地壳伸展因子是通过统计地震剖面上断层水平伸展量获得，介于1.678~2.238之间；全地壳伸展因子则采用拉伸前后地壳厚度之比的方法，分布在1.251~2.468之间；岩石圈伸展因子利用剖面二维反演回剥和正演伸展模拟得到的，分布在1.062~2.647之间。沿剖面方向不同圈层的伸展因子综合对比分析表明，琼东南盆地岩石圈发生了随深度变化的伸展，但并非简单的随深度增加，而可能与岩石圈不同层次的流变学特征及伸展前岩石圈流变性的不均匀性有关。
Abstract:In order to better understand the lithospheric extension process of the Qiongdongnan Basin, lithospheric stretching factors were calculated along the Line 1 which across both the continental shelf and slope. Upper-crust stretching factors were calculated by summing heaves measured on seismically imaged faults, varying from 1.678~2.238. Whole crust stretching factors changed from 1.251~2.468, derived from crustal-thinning constrained by seismic reflection and gravity inversion. Lithosphere stretching factors were determined from the combination of the two-dimensional flexural-cantilever forward and reverse modeling, ranging from 1.062~2.647. The results indicate that the depth dependent model is likely optional in the Qiongdongnan Basin. But the stretch factors are not simply increasing with depth, but also related to rheological features and the anisotropy of lithosphere before stretching.
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Key words:
- stretching factor β /
- 2D forward and reverse modeling /
- Qiongdongnan Basin
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表 1 YC21-1-3泥岩、砂岩百分比含量及各层沉积物颗粒密度PSG、孔隙度F、压实系数C
Table 1. Stratigraphic frame and lithologic parameters based on Well YC21-1-3
地震反射层 年龄/Ma 泥岩含量/% 砂岩含量/% 岩石颗粒密度/(kg/m3) 孔隙度 压实系数/(m-1) 第四系 T2 1.9 95.6 4.4 2 720 0.623 8 0.000 50 莺歌海组 T3 5.5 99.9 0.1 2 720 0.629 9 0.000 51 黄流组 T4 10.5 34.6 65.4 2 670 0.538 4 0.000 35 梅山组 T6 23 18.3 81.7 2 660 0.515 6 0.000 31 三亚组 T7 30 67.1 32.9 2 700 0.583 9 0.000 43 陵水组 T8 36 69 31 2 700 0.586 6 0.000 44 崖城组 Tg 50(?) 39.7 60.3 2 680 0.545 6 0.000 37 
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表 2 测线1断裂参数设置
Table 2. Fault parameters setting of Line 1
断层编号 X坐标/km 伸展量/km 倾角/(°) 倾向 1 9.708 3.263 43 右 2 16.155 2.049 37 右 4 28.252 2.002 28 左 5 39.970 1.214 40 左 6 47.402 1.290 34 左 7 56.276 1.159 80 右 8 67.880 1.593 60 左 9 91.278 2.428 32 左 10 106.712 5.118 31 左 11 111.490 1.290 54 右 12 115.283 1.214 48 右 13 120.857 1.366 73 右 14 129.465 3.263 22 左 15 133.257 3.490 36 右 16 146.378 2.124 36 右 17 163.216 2.945 31 右 19 170.421 3.552 15 右 20 178.119 1.214 43 右 21 186.462 1.062 35 右 22 197.725 1.138 50 左 23 202.503 1.935 18 右
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